Fix MarshalerUtil sizeRepeatedString calculation per issue#8272

[jhalliday]

The encoding of a zero length String as a single element is zero length (i.e. elided), but when encoded as an element of an array (i.e. 'repeated bytes' protobuf field) it's non-zero length, as space on the wire must still be used for the tag to denote the unoccupied location in the array.

[jack-berg]

Build will pass once you merge / rebase main.

[codecov]

Codecov Report

❌ Patch coverage is 33.33333% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.25%. Comparing base (ca41b47) to head (487c0cc).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
...metry/exporter/internal/marshal/MarshalerUtil.java	33.33%	1 Missing and 1 partial ⚠️

❌ Your patch status has failed because the patch coverage (33.33%) is below the target coverage (80.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #8284      +/-   ##
============================================
- Coverage     90.25%   90.25%   -0.01%     
- Complexity     7683     7684       +1     
============================================
  Files           850      850              
  Lines         23190    23191       +1     
  Branches       2353     2353              
============================================
  Hits          20930    20930              
  Misses         1533     1533              
- Partials        727      728       +1     

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