Add tests for some extensions currently not covered by the regression tests

[a-masterov]

Problem

Some extensions do not contain tests, which can be easily run on top of docker-compose or staging.

Summary of changes

Added the pg_regress based tests for pg_tiktoken, pgx_ulid, pg_rag
Now they will be run on top of docker-compose, but I intend to adopt them to be run on top staging in the next PRs

[github-actions]

7964 tests run: 7581 passed, 0 failed, 383 skipped (full report)

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Flaky tests (7)

Postgres 16

• test_pageserver_chaos[None]: release-x86-64-with-lfc
• test_remote_storage_backup_and_restore[False-real_s3]: release-x86-64-with-lfc
• test_remote_storage_backup_and_restore[True-real_s3]: release-x86-64-with-lfc
• test_tenant_s3_restore: release-x86-64-with-lfc

Postgres 15

• test_pageserver_restart: release-x86-64-with-lfc
• test_pg_regress[v2-4]: release-x86-64-with-lfc
• test_pg_regress[v1-4]: release-x86-64-with-lfc

Code coverage* (full report)

• functions: 32.3% (8734 of 27025 functions)
• lines: 48.4% (74876 of 154737 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
d5cbf29 at 2025-03-18T14:09:13.117Z :recycle:}

[Bodobolero]

The code looks fine.
The description of the PR says which can be easily run on top of docker-compose or staging.

I see that you added tests for the docker-compose path but maybe I overlooked it but I don't see that we test these in staging.
I think we shouldn't invest in further tests for extensions without making sure they really work in our cloud environment with neon_superuser derived postgres role neondb_owner.

If I overlooked it pls point me to where we verify the neon_superuser privileges work fine for these extensions.
We had too many customer reports for other extensions already thet "xxx" doesn't work for extension "yyy" because of missing privileges.

[a-masterov]

The code looks fine. The description of the PR says which can be easily run on top of docker-compose or staging.

I see that you added tests for the docker-compose path but maybe I overlooked it but I don't see that we test these in staging.

You didn't overlook, the test which can be run on top of staging is not yet ready. I plan to implement it soon using the same tests I added in this PR. I have updated the description to make it clear.

[Bodobolero]

Tests in staging will be done in separate PR, so I can approve this one, now