[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 97.96238% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 97.06%. Comparing base (bd998c7) to head (4250fda).

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/table_structure/zoo.py	92.59%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2092      +/-   ##
==========================================
+ Coverage   96.56%   97.06%   +0.49%     
==========================================
  Files         159      166       +7     
  Lines        7753     8387     +634     
==========================================
+ Hits         7487     8141     +654     
+ Misses        266      246      -20     

Flag	Coverage Δ
unittests	97.06% <97.96%> (+0.49%)	⬆️

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