Remove vector store experimental feature

[Strift]

Following this mega issue, we want to prepare for v1.13.0.

Description
Vector store and AI search become stable in v1.13.

Users should be able to use it without having to enable the experimental feature.

[ellnix]

The experimental settings endpoint methods have not been merged yet, so I fixed this on top of those PRs.

In any case, all of the experimental endpoints are dynamic, so changes are only required inside the tests.

[Strift]

hi @ellnix, the CI workflow requires us to make a PR against the bump-* branch to trigger the pre-release tests.

Thanks for your PR! I used it as a reference for #607.

I'm not fit to review the rest of the PR on the dynamicity of the endpoint, so it should remain in a separate PR for now.

Thanks again!