Support RDB v13

[moticless]

Add parsing support for RDB Version 13 (Redis 8.6). This includes:

Stream IDMP (Idempotent Message Producer) support:

• New encoded type RDB_TYPE_STREAM_LISTPACKS_4 for streams with IDMP data
• Parse IDMP metadata: duration, max entries, producers, and IID mappings
• New callbacks: handleStreamIdmpMeta, handleStreamIdmpProducer,
  handleStreamIdmpEntry
• RESP output generates XCFGSET and XIDMPRECORD commands for Redis 8.6+
• JSON output includes full IDMP structure when includeStreamMeta enabled

Key Metadata support:

• New opcode RDB_OPCODE_KEY_META (243) for module metadata classes
• Track numMeta count in RdbKeyInfo structure
• Add %m format specifier for print handler
• Serialize key metadata on RESTORE (L0). Otherwise discard it since
  metadata cannot be reconstructed without RESTORE command.

Testing:

• Stream v13: JSON output, RESP output (target 8.4 and 8.6), Redis reconstruct
  in both RESTORE (L0) and non-RESTORE (L1/L2) modes
• Key metadata: both RESTORE and non-RESTORE modes; verifies metadata
  preserved only via RESTORE
• Requires test_keymeta module for key metadata tests (auto-skipped if absent)

---

Note

High Risk
Touches the core RDB parsing state machine and RESP/JSON emitters to handle new v13 opcodes/types, which could regress parsing or serialization for existing dumps if edge cases are missed.

Overview
Adds RDB v13 (Redis 8.6) support by introducing the new stream encoding RDB_TYPE_STREAM_LISTPACKS_4 and parsing/propagating Stream IDMP (producer config + iid→stream-id mappings) via new data callbacks (handleStreamIdmpMeta/handleStreamIdmpProducer/handleStreamIdmpEntry). JSON output can now optionally include IDMP data (includeStreamIdmp), and RESP generation emits XCFGSET/XIDMPRECORD when targeting Redis 8.6+ (otherwise omits IDMP commands).

Adds parsing for the new key-metadata opcode RDB_OPCODE_KEY_META (243), tracks the per-key metadata class count (RdbKeyInfo.numMeta), preserves metadata only in raw/RESTORE mode (discarded at struct/data levels), and exposes it in print formatting via %m. Updates CLI/README help text and expands tests/fixtures for v13 streams, target-version RESP output, and key-metadata round-trips (auto-skipping when the test_keymeta module isn’t available).

^{Written by Cursor Bugbot for commit 17c22c8. This will update automatically on new commits. Configure here.}

[tezc]

I glanced over the PR but couldn't do a meaningful review yet. Tomorrow, I'll give it another go after taking a look at stream PR first but I doubt I'll be able to provide a meaningful review. Btw, if we can turn on Cursor in the repo, it will be more useful than me.

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

[oranagra]

approving based on previous reviews