K8SPG-822: add builtin-extensions e2e test

[pooknull]

https://perconadev.atlassian.net/browse/K8SPG-822

DESCRIPTION

This PR adds a builtin-extensions test that ensures extensions can be correctly enabled and disabled in the .spec.extensions.builtin section.

CHECKLIST

Jira

• Is the Jira ticket created and referenced properly?
• Does the Jira ticket have the proper statuses for documentation (Needs Doc) and QA (Needs QA)?
• Does the Jira ticket link to the proper milestone (Fix Version field)?

Tests

• Is an E2E test/test case added for the new feature/change?
• Are unit tests added where appropriate?

Config/Logging/Testability

• Are all needed new/changed options added to default YAML files?
• Are all needed new/changed options added to the Helm Chart?
• Did we add proper logging messages for operator actions?
• Did we ensure compatibility with the previous version or cluster upgrade process?
• Does the change support oldest and newest supported PG version?
• Does the change support oldest and newest supported Kubernetes version?

[valmiranogueira]

Can we also check the extension is working? By a select or something

Also it would be good to remove the test pgvector-extension

[pooknull]

d192ac8

ec5b6d1

[valmiranogueira]

Please check previous comment