Implement vector search experimental feature

[jackielii]

Pull Request

Related issue

Fixes #504

What does this PR do?

• [x] Ability to receive the embedders setting when calling the /indexes/:index_uid/settings route (GET/PATCH), so the methods to get and update global settings of an indexes should be adapted.
• [ ] Introduction of new routes
• [x] Create a new method to get the settings by calling GET /indexes/:index_uid/settings/embedders
• [x] Create a new method to update the settings by calling PATCH /indexes/:index_uid/settings/embedders
• [x] Create a new method to reset the settings by calling DELETE /indexes/:index_uid/settings/embedders
• [x] Introduction of a new parameter during the search: hybrid. It can take two fields: semanticRatio and embedder.
• [x] ⚠️ Tests should be added
• [x] Update README

PR checklist

Please check if your PR fulfills the following requirements:

• [x] Does this PR fix an existing issue, or have you listed the changes applied in the PR description (and why they are needed)?
• [x] Have you read the contributing guidelines?
• [x] Have you made sure that the title is accurate and descriptive of the changes?

Thank you so much for contributing to Meilisearch!

[jackielii]

There is only "Introduction of new routes" left which I'm not sure what to do. Otherwise the PR is ready.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 85.00000% with 6 lines in your changes are missing coverage. Please review.

Project coverage is 83.50%. Comparing base (9f390df) to head (dd9300a).

Files	Patch %	Lines
index_settings.go	82.35%	3 Missing and 3 partials :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #517 +/- ## ========================================== + Coverage 83.27% 83.50% +0.22% ========================================== Files 10 10 Lines 1543 1582 +39 ========================================== + Hits 1285 1321 +36 - Misses 146 147 +1 - Partials 112 114 +2 ```

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[meili-bors[bot]]

Build succeeded:

• integration-tests (go current version)
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