Improve throughput and resiliency of batching algo

[tsmith023]

• Removes locks from event loop
• Handles mapping async resp in batch thread instead of event loop thread to remove data locks in async fn
• Uses return of loop.schedule in batching thread to determine number of active requests without locks in async fn

Closes: #1332

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[codecov-commenter]

Codecov Report

Attention: Patch coverage is 75.81699% with 37 lines in your changes missing coverage. Please review.

Project coverage is 93.91%. Comparing base (3f68082) to head (a12c055).
Report is 138 commits behind head on main.

Files with missing lines	Patch %	Lines
weaviate/collections/batch/base.py	75.49%	37 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1371      +/-   ##
==========================================
- Coverage   94.38%   93.91%   -0.48%     
==========================================
  Files         220      221       +1     
  Lines       20956    21301     +345     
==========================================
+ Hits        19779    20004     +225     
- Misses       1177     1297     +120     

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[tsmith023]

Additional overhead of locking in the main batch looping thread and doing all CPU there slows down the logic considerably. Closing in favour of #1270