Add AI Search basic functional test coverage

Just getting started...

Okay ChatGPT managed to get ext-ffi required extension for the tests set up in gitlab CI... Means this approach using https://github.com/allanpichardo/mysql-vector as a simple way to test generating & querying embeddings will work fine.

Okay getting FFI to work was painful but now at least its a full end to end test of the basic functionality. Can add things like Boost in follow-ups. Things this revealed:

1. JS was required to deal with the ajax in the Search API Index form, that is now fixed here
2. Schema was invalid in some areas, that is now fixed here
3. Search API field indexing setup checker required JS, that is now fixed here
4. There was some potential inconsistencies in Search API Backend that could result in the distance not getting correctly calculated. Types are now fixed here

Changes look good and tests all passing.

This is now fixed. Added follow-up 📌 Remove composer require of dev release of Key module when Key makes a new release Postponed