Implement Bulk Update for FlatPostgresCollection

[suddendust]

Description

This PR implements Collection# bulkUpdate( final org.hypertrace.core.documentstore.query.Query query, final java.util.Collection<SubDocumentUpdate> updates, final UpdateOptions updateOptions) in FlatPostgresCollection.

Testing

Added integration tests.

Checklist:

• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• Any dependent changes have been merged and published in downstream modules

[codecov]

Codecov Report

❌ Patch coverage is 84.61538% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.01%. Comparing base (ef0d310) to head (a9ce511).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...documentstore/postgres/FlatPostgresCollection.java	84.61%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #278      +/-   ##
============================================
+ Coverage     80.98%   81.01%   +0.02%     
- Complexity        0     1446    +1446     
============================================
  Files           241      241              
  Lines          6954     6979      +25     
  Branches        643      648       +5     
============================================
+ Hits           5632     5654      +22     
- Misses          905      907       +2     
- Partials        417      418       +1     

Flag	Coverage Δ
integration	81.01% <84.61%> (+0.02%)	⬆️
unit	54.99% <65.38%> (+0.43%)	⬆️

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