feat: Add SearchApi integration

[SebastjanPrachovskij]

Proposed Changes:

• Added SearchApi as a providers
• Added SearchApi as a websearch component

How did you test it?

• Unit tests

Notes for the reviewer

• If you want to run e2e tests for SearchApi, let us know, and we'll give you credits.
• Feel free to assign @SebastjanPrachovskij as a main reviewer for any SearchApi-related PRs. We will be glad to help and support Haystack development.

Checklist

• I have read the contributors guidelines and the code of conduct
• I have updated the related issue with new insights and changes
• I added unit tests and updated the docstrings
• I've used one of the conventional commit types for my PR title: fix:, feat:, build:, chore:, ci:, docs:, style:, refactor:, perf:, test:.
• I documented my code
• I ran pre-commit hooks and fixed any issue

[github-actions]

This proposal is stale because it has been open 30 days with no activity. Remove stale label or comment or this will be closed in 10 days.