[TSR] Add TableCenterNet & table_predictor

[felixdittrich92]

This PR:

• Add TableCenterNet
• Add reference scripts
• Update docs
• Add table_predictor
• Add cor tests

[codecov]

Codecov Report

❌ Patch coverage is 97.64890% with 15 lines in your changes missing coverage. Please review.
✅ Project coverage is 97.04%. Comparing base (bd998c7) to head (34f7e9f).

Files with missing lines	Patch %	Lines
...octr/models/table_structure/tablecenternet/base.py	97.65%	7 Missing ⚠️
doctr/models/table_structure/predictor/pytorch.py	89.18%	4 Missing ⚠️
doctr/models/factory/hub.py	0.00%	2 Missing ⚠️
doctr/models/table_structure/zoo.py	92.59%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2092      +/-   ##
==========================================
+ Coverage   96.56%   97.04%   +0.47%     
==========================================
  Files         159      166       +7     
  Lines        7753     8387     +634     
==========================================
+ Hits         7487     8139     +652     
+ Misses        266      248      -18     

Flag	Coverage Δ
unittests	97.04% <97.64%> (+0.47%)	⬆️

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