[processor/tailsampling] Added debug logging to sampling decision caches

[portertech]

Description

This pull-request adds debug logging to the sampling decision caches, making it a little easier to debug decisions.

"Trace ID is in the sampled cache" and "Trace ID is in the non-sampled cache" with the trace ID as a zap field.

[codecov]

Codecov Report

Attention: Patch coverage is 33.33333% with 2 lines in your changes missing coverage. Please review.

Project coverage is 79.63%. Comparing base (333f016) to head (b59ddb2).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
processor/tailsamplingprocessor/processor.go	33.33%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #37038      +/-   ##
==========================================
- Coverage   79.63%   79.63%   -0.01%     
==========================================
  Files        2223     2223              
  Lines      210283   210285       +2     
==========================================
- Hits       167467   167464       -3     
- Misses      37206    37213       +7     
+ Partials     5610     5608       -2     

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