feat: add batch check telemetry attribute

[jimmyjames]

Description

Adds telemetry attribute fga-client.request.batch_check_size to capture number of checks in batch check request

References

Similar to openfga/js-sdk@59c000b

Review Checklist

• I have clicked on "allow edits by maintainers".
• I have added documentation for new/changed functionality in this PR or in a PR to openfga.dev [Provide a link to any relevant PRs in the references section above]
• The correct base branch is being used, if not main
• I have added tests to validate that the change in functionality is working as expected

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 83.33333% with 1 line in your changes missing coverage. Please review.

Project coverage is 32.82%. Comparing base (b7484e6) to head (baedf12).

Files with missing lines	Patch %	Lines
src/main/java/dev/openfga/sdk/api/OpenFgaApi.java	80.00%	0 Missing and 1 partial ⚠️

❌ Your project status has failed because the head coverage (32.82%) is below the target coverage (80.00%). You can increase the head coverage or adjust the target coverage.

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #143      +/-   ##
============================================
+ Coverage     32.78%   32.82%   +0.04%     
- Complexity      973      974       +1     
============================================
  Files           182      182              
  Lines          6872     6878       +6     
  Branches        764      766       +2     
============================================
+ Hits           2253     2258       +5     
  Misses         4512     4512              
- Partials        107      108       +1     

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[piotrooo]

LGFM