Add metric to track number of segments missed in upsert-snapshot

[tibrewalpratik17]

label:

• observability

Adding a metric to track number of segments missed in upsert-snapshot.

cc @ankitsultana

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 40.00000% with 3 lines in your changes are missing coverage. Please review.

Project coverage is 61.73%. Comparing base (59551e4) to head (e7fdc32).
Report is 89 commits behind head on master.

Files	Patch %	Lines
...cal/upsert/BasePartitionUpsertMetadataManager.java	25.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #12581      +/-   ##
============================================
- Coverage     61.75%   61.73%   -0.02%     
- Complexity      207      211       +4     
============================================
  Files          2436     2451      +15     
  Lines        133233   133730     +497     
  Branches      20636    20705      +69     
============================================
+ Hits          82274    82560     +286     
- Misses        44911    45073     +162     
- Partials       6048     6097      +49     

Flag	Coverage Δ
custom-integration1	<0.01% <0.00%> (-0.01%)	⬇️
integration	<0.01% <0.00%> (-0.01%)	⬇️
integration1	<0.01% <0.00%> (-0.01%)	⬇️
integration2	0.00% <0.00%> (ø)
java-11	61.70% <40.00%> (-0.01%)	⬇️
java-21	61.61% <40.00%> (-0.02%)	⬇️
skip-bytebuffers-false	61.72% <40.00%> (-0.03%)	⬇️
skip-bytebuffers-true	61.59% <40.00%> (+33.86%)	⬆️
temurin	61.73% <40.00%> (-0.02%)	⬇️
unittests	61.73% <40.00%> (-0.02%)	⬇️
unittests1	46.93% <20.00%> (+0.04%)	⬆️
unittests2	27.66% <20.00%> (-0.07%)	⬇️

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