Add `EngineArray` Multi-Model [1/3]

[michaelfeil]

• This feature is a work in progress to introduce a new concept: EngineArray
• this enables usage of multiple engines at the same time / multi-mdoel deployment

Closes #13

119

As a follow-up, need to make sure to launch multiple models via the CLI. This requires some refactoring of the cli. This is not part of this PR.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 88.52459% with 7 lines in your changes are missing coverage. Please review.

Project coverage is 73.60%. Comparing base (59a13c0) to head (6abebe1). Report is 4 commits behind head on main.

Files	Patch %	Lines
libs/infinity_emb/infinity_emb/engine.py	87.87%	4 Missing :warning:
libs/infinity_emb/infinity_emb/infinity_server.py	86.36%	3 Missing :warning:

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #200 +/- ## ========================================== + Coverage 73.49% 73.60% +0.11% ========================================== Files 32 32 Lines 1811 1849 +38 ========================================== + Hits 1331 1361 +30 - Misses 480 488 +8 ```

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