HDDS-15766. Make Recon OM DB large tarball transfer reliable

[devmadhuu]

What changes were proposed in this pull request?

Problem:
Recon keeps its own copy of the OM DB and syncs it two ways: incremental delta updates (getDBUpdates) for the normal case, and a full OM DB snapshot download as the fallback when delta sync cannot be used (Recon fell too far behind, OM no longer has the requested updates, etc.).

The full-snapshot fallback was the weak part:

• It used a single one-shot GET /dbCheckpoint call that streamed the entire OM DB as one tar.
• Any mid-stream failure restarted the download from byte 0.

On large clusters the OM DB is big, so this approach was slow and fragile.
Approach: Instead of maintaining Recon's own one-shot download logic, Recon now reuses the same bootstrap mechanism an OM follower uses to catch up from the OM leader:

• A chunked POST /v2/dbCheckpoint transfer. Each subsequent chunk carries a toExcludeList[] of the parts already received, so an interrupted transfer resumes instead of restarting from the beginning.
• The transfer is chunked and ends with a completion marker; the Recon client keeps the parts it already received and only requests the rest, so an interrupted transfer resumes instead of restarting.
• Resume/retry behavior comes from the shared, proven OM code path (RDBSnapshotProvider, the same base OmRatisSnapshotProvider uses) rather than a Recon-specific re-implementation.
• ReconRDBSnapshotProvider overrides only the download step and the step that assembles/promotes the finished DB.

What is the link to the Apache JIRA

https://issues.apache.org/jira/browse/HDDS-15766

How was this patch tested?

Testing:

• New unit tests TestReconRDBSnapshotProvider
• Updated TestOzoneManagerServiceProviderImpl— drives the new provider path for success and failure cases.
• Existing TestReconWithOzoneManager.testOmDBSyncWithSeqNumberMismatch provides end-to-end coverage of the full-snapshot fallback against a mini-cluster
• TestReconWithOzoneManagerHA updated to drop the stale v1-URL assertion, keeping its end-to-end leader-sync verification.