Return HTTP 410 for undelete on permanently deleted blob

[rcshaw]

Summary

Add a case for BlobDeletedPermanently in UndeleteOperation.processServerError, mapping it to RouterErrorCode.BlobDeleted so the frontend returns HTTP 410 Gone. Previously this server error code had no case in the switch and fell through to the default UnexpectedInternalError, surfacing as HTTP 500. A 410 (or any 4xx) is the correct semantic since the blob has been compacted and the undelete request can never succeed; clients should not retry.

Testing Done

Added blobDeletedPermanentlyTest in UndeleteManagerTest. Tests pass ./gradlew :ambry-router:test --tests "com.github.ambry.router.UndeleteManagerTest"

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 52.25%. Comparing base (52ba813) to head (fb0ba99).
⚠️ Report is 376 commits behind head on master.

Files with missing lines	Patch %	Lines
...ava/com/github/ambry/router/UndeleteOperation.java	0.00%	1 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             master    #3236       +/-   ##
=============================================
- Coverage     64.24%   52.25%   -11.99%     
+ Complexity    10398     8911     -1487     
=============================================
  Files           840      931       +91     
  Lines         71755    82074    +10319     
  Branches       8611    10436     +1825     
=============================================
- Hits          46099    42889     -3210     
- Misses        23004    35809    +12805     
- Partials       2652     3376      +724     

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[snalli]

Bouncing to retrigger CI on the new base (snalli/clustermap-test-flakes).

[snalli]

Reopened — CI should now run with the parallelized unit-test matrix + clustermap deflake fixes inherited from the new base.