fix: Fix string handling on bloom index Metadata Payload

[the-other-tim-brown]

Describe the issue this Pull Request addresses

Fixes a potential issue where strings can be UTF8 String in GenericRecord. This was handled for other payloads but not the bloom filter payload.

Summary and Changelog

Uses toString instead of casting

Impact

Fixes potential runtime issue

Risk Level

Low

Documentation Update

Contributor's checklist

• Read through contributor's guide
• Enough context is provided in the sections above
• Adequate tests were added if applicable

[the-other-tim-brown]

Both of these are required fields in the schema so there is no null check

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 57.27%. Comparing base (ec04479) to head (a9a39e8).
⚠️ Report is 988 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #18240      +/-   ##
============================================
- Coverage     61.43%   57.27%   -4.16%     
+ Complexity    23082    18533    -4549     
============================================
  Files          2108     1944     -164     
  Lines        127636   106132   -21504     
  Branches      14534    13118    -1416     
============================================
- Hits          78409    60791   -17618     
+ Misses        42873    39620    -3253     
+ Partials       6354     5721     -633     

Flag	Coverage Δ
hadoop-mr-java-client	45.41% <0.00%> (?)
spark-java-tests	47.43% <100.00%> (?)
spark-scala-tests	45.51% <100.00%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...rg/apache/hudi/metadata/MetadataPartitionType.java	71.02% <100.00%> (ø)

... and 4008 files with indirect coverage changes

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[hudi-bot]

CI report:

• a9a39e8 Azure: SUCCESS

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