Enable RAG tool when a vector DB is available

[TamiTakamiya]

Description

Enable RAG tool (builtin::rag/knowledge_search) when one or more vector DBs are defined on llama-stack.

Type of change

• Refactor
• New feature
• Bug fix
• CVE fix
• Optimization
• Documentation Update
• Configuration Update
• Bump-up service version
• Bump-up dependent library
• Bump-up library or tool used for development (does not change the final image)
• CI configuration change
• Konflux configuration change
• Unit tests improvement
• Integration tests improvement
• End to end tests improvement

Related Tickets & Documents

• Related Issue # n/a
• Closes # n/a

Checklist before requesting a review

• I have performed a self-review of my code.
• PR has passed all pre-merge test jobs.
• If it is a core feature, I have added thorough tests.

Testing

• Please provide detailed steps to perform tests related to this code change.
• How were the fix/results from this change verified? Please provide relevant screenshots or results.

[manstis]

LGTM 👍

@tisnik we need this.

[tisnik]

it looks ok, just one nitpick - we can use list as type hint, that does not have to be imported

[umago]

Thanks Tami! Code-wise it does LGTM except the nit that Pavel already pointed out.

Thanks for working on this, we very much need it!

[tisnik]

it looks perfect, TYVM