ref(spans): Reorganize the segment consumer code

[jan-auer]

Moves enrichment into a dedicated module and improves typing of Spans passed
around in the factory. This should make it more clear, at which stage the spans
have been enriched.

[codecov]

Codecov Report

Attention: Patch coverage is 92.85714% with 9 lines in your changes missing coverage. Please review.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...try/spans/consumers/process_segments/enrichment.py	85.93%	9 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #87481   +/-   ##
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  Coverage   87.73%   87.73%           
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  Files        9891     9895    +4     
  Lines      560996   561057   +61     
  Branches    22136    22136           
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+ Hits       492198   492259   +61     
  Misses      68394    68394           
  Partials      404      404