Add an overridable table-config-change callback distinct from index-loading-config fetch

[krishan1390]

The server's table-config/schema refresh message handler called fetchIndexLoadingConfig() purely for its cache-refresh side effect, discarding the returned config. That same fetchIndexLoadingConfig() is also invoked incidentally during segment state transitions and reloads, so a table data manager had no way to distinguish "the config actually changed" from "an index loading config was fetched while a transition was in progress."

This adds a dedicated onTableConfigOrSchemaRefresh() callback on TableDataManager. The default implementation refreshes the cached table config and schema (preserving today's behavior), and the refresh message handler now invokes the callback instead of fetchIndexLoadingConfig(). The behavior of fetchIndexLoadingConfig() during transitions is unchanged. This gives implementations a hook that fires only on a genuine config/schema change.

Testing

BaseTableDataManagerTest#testOnTableConfigOrSchemaRefreshRefreshesCachedConfig verifies the default callback refreshes the cached config/schema. Existing data-manager and server tests pass.

🤖 Generated with Claude Code

[krishan1390]

No blocking issues found in review.

[krishan1390]

Minor (non-blocking): the concrete @Override onTableConfigOrSchemaRefresh() in BaseTableDataManager has the same body as the interface default (fetchIndexLoadingConfig()), so it is technically redundant. Keeping it is defensible as a discoverable extension seam alongside the other @Overrides, but you could drop it and rely solely on the default if you prefer less duplication. Either is fine. Javadoc, wiring, back-compat, and the test all look good.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 40.00000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 64.80%. Comparing base (b6b3b6c) to head (9f99abf).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
...t/segment/local/data/manager/TableDataManager.java	0.00%	2 Missing ⚠️
...er/starter/helix/SegmentMessageHandlerFactory.java	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #18792      +/-   ##
============================================
+ Coverage     64.78%   64.80%   +0.01%     
  Complexity     1309     1309              
============================================
  Files          3380     3380              
  Lines        209630   209634       +4     
  Branches      32822    32822              
============================================
+ Hits         135817   135843      +26     
+ Misses        62883    62860      -23     
- Partials      10930    10931       +1     

Flag	Coverage Δ
custom-integration1	100.00% <ø> (ø)
integration	100.00% <ø> (ø)
integration1	100.00% <ø> (ø)
integration2	0.00% <ø> (ø)
java-21	64.80% <40.00%> (+0.01%)	⬆️
temurin	64.80% <40.00%> (+0.01%)	⬆️
unittests	64.79% <40.00%> (+0.01%)	⬆️
unittests1	56.98% <50.00%> (+0.01%)	⬆️
unittests2	37.27% <0.00%> (+<0.01%)	⬆️

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