HDDS-14432. SnapshotDeletingService incorrectly checks Ratis Buffer Limit

[aswinshakil]

What changes were proposed in this pull request?

SnapshotDeletingService incorrectly checks the Ratis Buffer Limit when we invoke submitSnapshotMoveDeletedKeys , it adds all the keys to the builder and then checks the size of the message. Later, it again adds more deletedKeys, deletedDirs and renamedKeys on it, The message size is already over the ratis buffer limit, instead of creating a new builder we re-use the same builder. Ideally we should stop iterating through the snapshot-related tables when we hit the buffer limit even before going to submitSnapshotMoveDeletedKeys

What is the link to the Apache JIRA

https://issues.apache.org/jira/browse/HDDS-14432

How was this patch tested?

Existing Tests

[Copilot]

Pull request overview

This PR fixes incorrect Ratis buffer limit checking in SnapshotDeletingService. The old implementation would add all snapshot-related entries to a request builder before checking if the message size exceeded the buffer limit, then attempted to recover by truncating the lists. This approach was flawed as it could create oversized messages.

Changes:

• Replaced the flawed size-checking logic with progressive batch building that checks size limits before adding each entry
• Introduced proper batching across deletedKeys, renamedKeys, and deletedDirs with early termination on failures
• Improved error handling by returning the count of successfully submitted entries for accurate retry tracking

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[smengcl]

lgtm. Could you add a test case for this fix? (which would have failed without this fix)