[DRAFT] [DO NOT MERGE] Entities support prototype

[dmitryax]

Recreated #11282

[codecov]

Codecov Report

Attention: Patch coverage is 39.98768% with 974 lines in your changes missing coverage. Please review.

Project coverage is 88.33%. Comparing base (50104db) to head (8ae874d).

Files with missing lines	Patch %	Lines
service/internal/builders/connector.go	0.00%	126 Missing ⚠️
pdata/pentity/entities.go	0.00%	86 Missing ⚠️
connector/xconnector/connector.go	0.00%	84 Missing ⚠️
...xporter/exporterhelper/xexporterhelper/entities.go	0.00%	81 Missing ⚠️
pdata/pentity/json.go	0.00%	70 Missing ⚠️
internal/fanoutconsumer/entities.go	0.00%	41 Missing ⚠️
pdata/pentity/pentityotlp/response.go	0.00%	41 Missing ⚠️
pdata/pentity/pentityotlp/request.go	0.00%	30 Missing ⚠️
service/internal/graph/connector.go	0.00%	29 Missing ⚠️
...porter/debugexporter/internal/otlptext/entities.go	6.89%	27 Missing ⚠️
... and 34 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #11958      +/-   ##
==========================================
- Coverage   91.62%   88.33%   -3.30%     
==========================================
  Files         447      477      +30     
  Lines       23731    25335    +1604     
==========================================
+ Hits        21743    22379     +636     
- Misses       1613     2564     +951     
- Partials      375      392      +17     

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