PointerNetworkTaskModuleForEnd2EndRE: outsource remaining encoder-decoder specific logic

[ArneBinder]

Move all remaining logic that is specific to the relation_encoder_decoder into BinaryRelationEncoderDecoder, i.e., the creation of constraints and parsing of partial / erroneous encodings.

This PR:

• adds the interface methods to AnnotationEncoderDecoder:
  • build_decoding_constraints
  • parse
• adds implements to BinaryRelationEncoderDecoder
• in PointerNetworkTaskModuleForEnd2EndRE:
  • removes build_constraints but uses self.relation_encoder_decoder.build_decoding_constraints (in ._build_constraint) instead
  • removes decode_relations but uses self.relation_encoder_decoder.parse instead

Note that the implementations of BinaryRelationEncoderDecoder.build_decoding_constraints and .parse are not complete, they do not cover all options for mode and do not work with arbitrary head_encoder_decoder / tail_encoder_decoder. But they cover the same amount of features that were implemented until now.

This is a first step for a simplified version of #63. Especially, it is not breaking. Remaining steps would be:

• implement MultiSpanEncoderDecoder,
• adjust _post_prepare to use it as relation_encoder_decoder (if the layer of document_type with span_layer_name is of type LabeledMultiSpan), and
• adjust cmp_src_rel (relation sorting) to work with LabeledMultiSpan.
• (optional: add reversed relations logic)

This will also allow to use this taskmodule as a blueprint for pointer based setups that handle any annotation structures. This will require to overwrite:

• _post_prepare,
• encode_annotations, and
• decode_annotations.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 95.93496% with 5 lines in your changes missing coverage. Please review.

Project coverage is 95.85%. Comparing base (aba3467) to head (ececb53).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...ules/pointer_network/annotation_encoder_decoder.py	96.05%	3 Missing ⚠️
...ules/taskmodules/pointer_network_for_end2end_re.py	95.55%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #181      +/-   ##
==========================================
- Coverage   95.88%   95.85%   -0.03%     
==========================================
  Files          68       68              
  Lines        6071     6107      +36     
==========================================
+ Hits         5821     5854      +33     
- Misses        250      253       +3     

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