feat(java): complete GraphAr metadata API parity

[keksmd]

Reason for this PR

Completes the dependency-light Java metadata API compatibility work tracked by #955 and relates to the metadata-round-trip umbrella #944. The PR is deliberately limited to graphar-info; it adds no physical IO, storage, Arrow, or query-engine dependency.

What changes are included in this PR?

• Preserves GraphAr graph labels, extra_info, and typed list<T> values through YAML loading and saving.
• Adds indexed metadata/property-group lookup and immutable property-group removal.
• Gives Property and PropertyGroup value equality and hash codes, so removal works for an equivalent deserialized property group rather than only the same object reference.
• Makes invalid indexed lookups consistently throw IllegalArgumentException, matching existing Java lookup APIs.
• Adds YAML round-trip, list-type, value-semantic, removal, and index-boundary tests.

Are these changes tested?

Yes, against current upstream/main with GAR_TEST_DATA=testing:

• mvn --no-transfer-progress -P!nexus-download -pl info -am spotless:check
• mvn --no-transfer-progress -P!nexus-download -pl info -am clean verify -Dspotless.check.skip=true — 133 tests, 0 failures/errors/skips.
• pre-commit run --files for all 23 changed Java files, and git diff --check.

Are there any user-facing changes?

Yes. The Java metadata API gains immutable lookup/removal and full GraphAr metadata round-trip support; no on-disk topology or storage behavior changes.

Checklist

• I have performed a self-review of my own code.
• I have formatted my own code using make cpplint before submitting when changed files are in the cpp directory.
• I have performed pre-commit run before commit the changed files.
• I have added tests to prove my changes are effective.

[SemyonSinchenko]

For me it looks like without equals for PropertyGroup it won't work correctly.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 82.26950% with 25 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.59%. Comparing base (0a51cd2) to head (91018d0).

Files with missing lines	Patch %	Lines
...in/java/org/apache/graphar/info/type/DataType.java	74.19%	2 Missing and 6 partials ⚠️
...in/java/org/apache/graphar/info/PropertyGroup.java	68.42%	1 Missing and 5 partials ⚠️
...c/main/java/org/apache/graphar/info/GraphInfo.java	80.00%	3 Missing and 2 partials ⚠️
...rc/main/java/org/apache/graphar/info/Property.java	66.66%	1 Missing and 3 partials ⚠️
...pache/graphar/info/loader/BaseGraphInfoLoader.java	90.00%	1 Missing ⚠️
...in/java/org/apache/graphar/info/type/FileType.java	75.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #956      +/-   ##
============================================
+ Coverage     77.40%   77.59%   +0.18%     
- Complexity      621      682      +61     
============================================
  Files            84       85       +1     
  Lines          8972     9091     +119     
  Branches       1074     1098      +24     
============================================
+ Hits           6945     7054     +109     
+ Misses         1785     1780       -5     
- Partials        242      257      +15     

Flag	Coverage Δ
java-info	85.48% <82.26%> (+0.59%)	⬆️

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[keksmd]

@SemyonSinchenko спасибо за конкретные замечания — все три исправил в 91018d0:

• Property и PropertyGroup теперь имеют value-based equals/hashCode; immutable removal принимает эквивалентную property group, а не только тот же object reference.
• Некорректный index в Graph/Vertex/Edge metadata теперь бросает IllegalArgumentException, как существующие Java lookup API.
• PR перебазирован на текущий main, уже включающий fix(java): align edge metadata paths with GraphAr v1 #946 и fix(cpp): restore Arrow 17 devcontainer compatibility #952.

Заодно объединил это с близким metadata round-trip slice: labels, extra_info и typed list<T> теперь сохраняются через YAML. Локально graphar-info проходит 133 теста; upstream title/pre-commit/license уже зелёные, Java-info job ещё ожидает запуска.

Отдельно открыл небольшой независимый Java API PR #958 (issue #957): только storage interfaces, без adapter implementation и без зависимости от этого PR. Буду рад твоему ревью, когда будет время.

[SemyonSinchenko]

~LGTM

[SemyonSinchenko]

@SYaoJun @yangxk1 @Thespica Hi! Let's merge this one? LGTM overall. GAR Java is not published, so there cannot be any breaking changes and it is safe to merge imo.