Bringing in EPLabs AI Features

[ZacharyRener]

Description of the Change

Partially completes #4316

This is the base level of bringing over the AI features from EP Labs to EP.

• Brings the three features over along with their full tests
• Condenses Search Algorithm feature into Semantic Search
  • Three kNN options available for selection, hybrid as default
• Ensures ElasticPress AI Features take precedence over the EP Labs ones if both are activated (see includes/classes/FeaturePrecedence.php: https://github.com/10up/ElasticPress/pull/4317/changes#diff-34d0b851a32698730828a97808b880d70d874bee8afdcde89af30875c605fab7

How to test the Change

• Install both ElasticPress and ElasticPress Labs
• Deactivate ElasticPress Labs, and verify the three AI Features remain available
• Verify that the search algorithm options only show under Semantic Search, and not Other => Search Algorithms
• Activate ElasticPress Labs, and verify that the ElasticPress AI features still take precedence:
  • Search algorithms should still be under Semantic Search
  • Other => Search Algorithms should still be removed
  • elasicpress-labs/ai-search-summary block should not be available

Changelog Entry

Added - AI Feature: Semantic Search
Added - AI Feature: Vector Embeddings
Added - AI Feature: AI Search Results

Credits

Props @felipeelia, @ZacharyRener

Checklist:

• I agree to follow this project's Code of Conduct.
• I have updated the documentation accordingly.
• I have added Critical Flows, Test Cases, and/or End-to-End Tests to cover my change.
• All new and existing tests pass.

[ZacharyRener]

This portion is ready for review @felipeelia