PointerNetworkTaskModuleForEnd2EndRE: skip duplicated / conflicting relations during encoding

[ArneBinder]

• skip relation when another relation with same arguments and same label was already encoded
• skip whole task encoding if another relation with same arguments and a different label was already encoded

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 85.71429% with 1 line in your changes missing coverage. Please review.

Project coverage is 95.52%. Comparing base (a440655) to head (8d4b1e3).

Files with missing lines	Patch %	Lines
...ules/taskmodules/pointer_network_for_end2end_re.py	85.71%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #146      +/-   ##
==========================================
+ Coverage   95.45%   95.52%   +0.06%     
==========================================
  Files          61       61              
  Lines        5127     5134       +7     
==========================================
+ Hits         4894     4904      +10     
+ Misses        233      230       -3     

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