perf(resource-packs): cache converted packs by content

[AlexProgrammerDE]

What this changes

Converting a resource-pack stack on every join repeats expensive ZIP work and can advertise stale output when the pack content changes. Cache conversions by the effective pack stack and content hash, and verify cached ZIPs before reuse.

Write converted packs and their index atomically, give identical content a stable advertised hash and ID, and make ZIP entry order deterministic. Encode ResourcePackClientResponse with the current varint pack-list count; the old 16-bit count breaks game-protocol downloads. Add focused cache, load-state, and packet-layout tests. Based on ViaBedrock PR #420.

This is the current north-star feature from StackAnvil's viabedrock patch stack. The PR branch contains this feature alone, based on upstream.

Review focus

Please check that a changed source pack cannot reuse an older conversion, and that reconnecting with unchanged packs avoids another conversion.

Testing

• Run ./gradlew test checkstyleMain checkstyleTest on the feature-only checkout.
• Join Bedrock Dedicated Server 1.26.51.1 with a resource pack, reconnect, and confirm the converted pack is reused.
• Change the pack texture and version, then confirm a new conversion contains the changed bytes and the Java client loads it.
• Join the same server with Fabulously Optimized after the cache checks.

The live joins used the full StackAnvil patch stack and a local ViaProxy build compatible with the current ViaBedrock API.