Run the extensions' tests on staging (#11164)

## Problem
We currently don't run end-to-end tests for PostgreSQL extensions on our
cloud infrastructure, which means we might miss problems that only occur
in a real cloud environment.

## Summary of changes
- Added a workflow to run extension tests against a cloud staging
instance
- Set up proper project configuration for extension testing
- Implemented test execution with appropriate environment settings
- Added error handling and reporting for test failures

---------

Co-authored-by: Alexander Bayandin <alexander@neon.tech>
Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

docker-compose/ext-src/pg_graphql-src/regular-test.sh

@@ -0,0 +1,23 @@
+#!/bin/bash
+set -ex
+cd "$(dirname "${0}")"
+PGXS="$(dirname "$(pg_config --pgxs)" )"
+REGRESS="${PGXS}/../test/regress/pg_regress"
+TESTDIR="test"
+TESTS=$(ls "${TESTDIR}/sql" | sort )
+TESTS=${TESTS//\.sql/}
+TESTS=${TESTS/empty_mutations/}
+TESTS=${TESTS/function_return_row_is_selectable/}
+TESTS=${TESTS/issue_300/}
+TESTS=${TESTS/permissions_connection_column/}
+TESTS=${TESTS/permissions_functions/}
+TESTS=${TESTS/permissions_node_column/}
+TESTS=${TESTS/permissions_table_level/}
+TESTS=${TESTS/permissions_types/}
+TESTS=${TESTS/row_level_security/}
+TESTS=${TESTS/sqli_connection/}
+dropdb --if-exist contrib_regression
+createdb contrib_regression
+psql -v ON_ERROR_STOP=1 -f test/fixtures.sql -d contrib_regression
+${REGRESS} --use-existing --dbname=contrib_regression --inputdir=${TESTDIR} ${TESTS}
+