[ISSUE #10879] fix(tieredstore): refresh replaced topic metadata timestamp

[yuluo-yx]

Which Issue(s) This PR Fixes

• Fixes [Bug] Replacing topic metadata preserves a stale update timestamp #10879

Brief Description

DefaultMetadataStore.updateTopic now refreshes the timestamp on the caller-provided TopicMetadata that is actually stored, instead of mutating the old object immediately before replacing it.

How Did You Test This Change?

• mise exec java@zulu-8.94.0.17 -- mvn -pl tieredstore -am -DskipITs -Dtest=DefaultMetadataStoreTest -Dsurefire.failIfNoSpecifiedTests=false test (7 tests passed)
• Checkstyle and SpotBugs passed in the same Maven reactor.
• git diff --check and the 400-line scope gate passed.
• Not run: full repository build, container tests, or end-to-end tests.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 48.29%. Comparing base (fd0c959) to head (c9df15c).

Additional details and impacted files

@@              Coverage Diff              @@
##             develop   #10889      +/-   ##
=============================================
- Coverage      48.39%   48.29%   -0.10%     
+ Complexity     13562    13525      -37     
=============================================
  Files           1380     1380              
  Lines         101165   101165              
  Branches       13127    13127              
=============================================
- Hits           48962    48862     -100     
- Misses         46233    46305      +72     
- Partials        5970     5998      +28     

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[RockteMQ-AI]

LGTM. Trivial change, looks good.

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