PG18 compatibility: misc output diffs pt2 (#8234)

3 minor changes to reduce some noise from the regression diffs.

1 - Reduce verbosity when ALTER EXTENSION fails
PG18 has improved reporting of errors in extension script files
Relevant PG commit:
https://github.com/postgres/postgres/commit/774171c4f
There was more context in PG18, so reducing verbosity
```
ALTER EXTENSION citus UPDATE TO '11.0-1';
 ERROR:  cstore_fdw tables are deprecated as of Citus 11.0
 HINT:  Install Citus 10.2 and convert your cstore_fdw tables to the
        columnar access method before upgrading further
 CONTEXT:  PL/pgSQL function inline_code_block line 4 at RAISE
+SQL statement "DO LANGUAGE plpgsql
+$$
+BEGIN
+    IF EXISTS (SELECT 1 FROM pg_dist_shard where shardstorage = 'c') THEN
+     RAISE EXCEPTION 'cstore_fdw tables are deprecated as of Citus 11.0'
+        USING HINT = 'Install Citus 10.2 and convert your cstore_fdw tables
                       to the columnar access method before upgrading further';
+ END IF;
+END;
+$$"
+extension script file "citus--10.2-5--11.0-1.sql", near line 532
```

2 - Fix backend type order in tests for PG18
PG18 added another backend type which messed the order
in this test
Adding a separate IF condition for PG18
Relevant PG commit:
https://github.com/postgres/postgres/commit/18d67a8d7d

3 - Ignore "DEBUG: find_in_path" lines in output
Relevant PG commit:
https://github.com/postgres/postgres/commit/4f7f7b0375
The new GUC extension_control_path specifies a path to look for
extension control files.

src/test/regress/bin/normalize.sed

@@ -365,3 +365,7 @@ s/^([ \t]*)List of sequences$/\1List of relations/g
 s/violates RESTRICT setting of foreign key constraint/violates foreign key constraint/g
 # DETAIL line changed "is referenced" -> old "is still referenced"
 s/\<is referenced from table\>/is still referenced from table/g
+
+# pg18 extension_control_path GUC debugs
+# ignore any "find_in_path:" lines in test output
+/DEBUG:  find_in_path: trying .*/d

src/test/regress/expected/multi_extension.out

@@ -1120,10 +1120,11 @@ DROP TABLE columnar_schema_members, columnar_schema_members_pg_depend;
 -- Use a synthetic pg_dist_shard record to show that upgrade fails
 -- when there are cstore_fdw tables
 INSERT INTO pg_dist_shard (logicalrelid, shardid, shardstorage) VALUES ('pg_dist_shard', 1, 'c');
+-- reduce verbosity since there is more context in PG18 (774171c4f)
+\set VERBOSITY terse
 ALTER EXTENSION citus UPDATE TO '11.0-1';
 ERROR:  cstore_fdw tables are deprecated as of Citus 11.0
-HINT:  Install Citus 10.2 and convert your cstore_fdw tables to the columnar access method before upgrading further
-CONTEXT:  PL/pgSQL function inline_code_block line XX at RAISE
+\set VERBOSITY default
 DELETE FROM pg_dist_shard WHERE shardid = 1;
 -- partitioned table count is tracked on Citus 11 upgrade
 CREATE TABLE e_transactions(order_id varchar(255) NULL, transaction_id int) PARTITION BY LIST(transaction_id);
@@ -1510,11 +1511,11 @@ SELECT create_distributed_table('null_shard_key', null);
 
 -- Show that we cannot downgrade to 11.3-2 becuase the cluster has a
 -- distributed table with single-shard.
+-- reduce verbosity since there is more context in PG18 (774171c4f)
+\set VERBOSITY terse
 ALTER EXTENSION citus UPDATE TO '11.3-2';
 ERROR:  cannot downgrade Citus because there are distributed tables without a shard key.
-DETAIL:  To downgrade Citus to an older version, you should first convert those tables to Postgres tables by executing SELECT undistribute_table("%s").
-HINT:  You can find the distributed tables without a shard key in the cluster by using the following query: "SELECT * FROM citus_tables WHERE distribution_column = '<none>' AND colocation_id > 0".
-CONTEXT:  PL/pgSQL function inline_code_block line XX at RAISE
+\set VERBOSITY default
 DROP TABLE null_shard_key;
 ALTER EXTENSION citus UPDATE TO '11.3-2';
 -- Should be empty result since upgrade+downgrade should be a no-op

src/test/regress/expected/multi_mx_hide_shard_names.out

@@ -476,11 +476,18 @@ SELECT relname FROM pg_catalog.pg_class WHERE relnamespace = 'mx_hide_shard_name
 -- Relevant PG16 commit:
 -- https://github.com/postgres/postgres/commit/0c679464a837079acc75ff1d45eaa83f79e05690
 -- Relevant Pg17 commit:
--- https://github.com/postgres/postgres/commit/067701f57758f9baed5bd9d868539738d77bfa92#diff-afc0ebd67534b71b5b94b29a1387aa6eedffe342a5539f52d686428be323e802
+-- https://github.com/postgres/postgres/commit/067701f57758f9baed5bd9d868539738d77bfa92
+-- Relevant PG18 commit:
+-- https://github.com/postgres/postgres/commit/18d67a8d7d30884655d65910b82781d9360819a6
 SHOW server_version \gset
+SELECT substring(:'server_version', '\d+')::int >= 18 AS server_version_ge_18 \gset
 SELECT substring(:'server_version', '\d+')::int >= 17 AS server_version_ge_17 \gset
 SELECT substring(:'server_version', '\d+')::int >= 16 AS server_version_ge_16 \gset
-\if :server_version_ge_17
+\if :server_version_ge_18
+  SELECT 1 AS client_backend \gset
+  SELECT 5 AS bgworker \gset
+  SELECT 6 AS walsender \gset
+\elif :server_version_ge_17
   SELECT 1 AS client_backend \gset
   SELECT 4 AS bgworker \gset
   SELECT 5 AS walsender \gset

src/test/regress/sql/multi_extension.sql

@@ -534,7 +534,10 @@ DROP TABLE columnar_schema_members, columnar_schema_members_pg_depend;
 -- Use a synthetic pg_dist_shard record to show that upgrade fails
 -- when there are cstore_fdw tables
 INSERT INTO pg_dist_shard (logicalrelid, shardid, shardstorage) VALUES ('pg_dist_shard', 1, 'c');
+-- reduce verbosity since there is more context in PG18 (774171c4f)
+\set VERBOSITY terse
 ALTER EXTENSION citus UPDATE TO '11.0-1';
+\set VERBOSITY default
 DELETE FROM pg_dist_shard WHERE shardid = 1;
 
 -- partitioned table count is tracked on Citus 11 upgrade
@@ -699,7 +702,10 @@ SELECT create_distributed_table('null_shard_key', null);
 
 -- Show that we cannot downgrade to 11.3-2 becuase the cluster has a
 -- distributed table with single-shard.
+-- reduce verbosity since there is more context in PG18 (774171c4f)
+\set VERBOSITY terse
 ALTER EXTENSION citus UPDATE TO '11.3-2';
+\set VERBOSITY default
 
 DROP TABLE null_shard_key;
 

src/test/regress/sql/multi_mx_hide_shard_names.sql

@@ -249,11 +249,18 @@ SELECT relname FROM pg_catalog.pg_class WHERE relnamespace = 'mx_hide_shard_name
 -- Relevant PG16 commit:
 -- https://github.com/postgres/postgres/commit/0c679464a837079acc75ff1d45eaa83f79e05690
 -- Relevant Pg17 commit:
--- https://github.com/postgres/postgres/commit/067701f57758f9baed5bd9d868539738d77bfa92#diff-afc0ebd67534b71b5b94b29a1387aa6eedffe342a5539f52d686428be323e802
+-- https://github.com/postgres/postgres/commit/067701f57758f9baed5bd9d868539738d77bfa92
+-- Relevant PG18 commit:
+-- https://github.com/postgres/postgres/commit/18d67a8d7d30884655d65910b82781d9360819a6
 SHOW server_version \gset
+SELECT substring(:'server_version', '\d+')::int >= 18 AS server_version_ge_18 \gset
 SELECT substring(:'server_version', '\d+')::int >= 17 AS server_version_ge_17 \gset
 SELECT substring(:'server_version', '\d+')::int >= 16 AS server_version_ge_16 \gset
-\if :server_version_ge_17
+\if :server_version_ge_18
+  SELECT 1 AS client_backend \gset
+  SELECT 5 AS bgworker \gset
+  SELECT 6 AS walsender \gset
+\elif :server_version_ge_17
   SELECT 1 AS client_backend \gset
   SELECT 4 AS bgworker \gset
   SELECT 5 AS walsender \gset