HDDS-16363. Fix split-schema MPU size tracking in Recon event handlers

[priyeshkaratha]

What changes were proposed in this pull request?

Problem:
The Recon API endpoint /api/v1/keys/open/mpu/summary was returning zero sizes for split-schema multipart uploads (MPUs) because event handlers were not tracking part sizes from the multipartPartsTable. Only legacy-schema MPU sizes
(embedded in multipartInfoTable values) were tracked by events. Split-schema MPU sizes were only calculated during periodic reprocess, causing newly created split-schema MPUs to show zero sizes until the next reprocess run.

Root Cause:
When split-schema MPU support was added (HDDS-14666), the MultipartInfoInsightHandler event methods were updated to use forEachLegacyPart(), which returned early for split-schema MPUs without processing any sizes. Event handlers had no mechanism to access multipartPartsTable to fetch split-schema part sizes incrementally.

Solution:

1. Extended OmTableHandler interface to pass OMMetadataManager to event handlers, enabling access to multipartPartsTable during event processing.

2. Added new applySplitSchemaPartSizes() method to MultipartInfoInsightHandler that:

   • Queries multipartPartsTable for all parts of a split-schema MPU
   • Calculates unreplicated and replicated sizes for each part
   • Updates size maps on PUT/DELETE/UPDATE events immediately

3. Integrated split-schema size tracking into PUT, DELETE, and UPDATE event handlers.

4. Updated DeletedKeysInsightHandler and OpenKeysInsightHandler to accept the new OMMetadataManager parameter (no-op for these handlers).

What is the link to the Apache JIRA

HDDS-16363

How was this patch tested?

• Added new test testProcessForSplitSchemaMPU() to verify split-schema MPU sizes are calculated immediately on PUT/DELETE events without waiting for reprocess.
• Test creates split-schema MPU with 3 parts of 100 bytes each, verifies:
  • PUT event results in correct sizes: 300 bytes unreplicated, 900 bytes replicated
  • DELETE event resets sizes to 0
• All 14 existing tests continue to pass.

Tested manually