Optimize batch-read to avoid wasted disk IO

[dao-jun]

Motivation

Batch reads currently fetch the next entry before checking whether it can still fit within the maxSize budget. When the last entry in the batch exceeds the remaining space, the read result is discarded, but the disk IO has already happened. This creates wasted IO on the critical read path.

This change avoids that extra read while preserving the existing batch-read behavior, including returning the first entry even when a single entry alone exceeds the requested maxSize.

Changes

• Add a bounded-read path (readEntryIfFits / getEntryIfFits) through the batch-read stack, from BatchedReadEntryProcessor down to Bookie, LedgerDescriptor, LedgerStorage, and EntryLogger.
• Update batch-read logic to:
  • read the first entry as before
  • compute the remaining response budget for subsequent entries
  • stop without reading the next entry when it cannot fit
• Implement size-aware entry reads in both DefaultEntryLogger and DirectEntryLogger by checking entry size from metadata before loading the full payload.
• Wire the bounded-read path through all storage implementations, including:
  • InterleavedLedgerStorage
  • SortedLedgerStorage
  • DbLedgerStorage / SingleDirectoryDbLedgerStorage
• Keep framing semantics consistent by treating the per-entry 4-byte delimiter as part of the size budget.
• Update mock batch-read behavior to match the production semantics.
• Add regression and boundary tests covering:
  • first entry larger than maxSize
  • exact-fit remaining budget
  • oversized subsequent entries
  • default entry logger and direct entry logger paths
  • interleaved, sorted, and DB ledger storage paths
  • mock and client-facing batch-read behavior

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[eolivelli]

I can't find tests about failure scenarios.

Memory leaks can happen in case of failures (reading from storage...), client may see the wrong error code.....

[dao-jun]

@eolivelli I added 3 tests in BatchedReadEntryProcessorTest, PTAL