[enhance]: support multiple gRPC compression algorithms and configurable zstd codec

Summary

Enhance Milvus's internal gRPC compression:

• Support multiple compression algorithms: zstd (existing), snappy, and s2.
• Make the zstd compression level configurable via 4 coarse tiers (fastest / default / better / best), defaulting to default.
• Add a zstd per-frame CRC32 checksum toggle (grpc.client.compressionCRC, default false).
• Scale the zstd codec concurrency with the tier (tier × GOMAXPROCS) and reuse compressed buffers via a bounded pool (capped at 2 × GOMAXPROCS).
• Upgrade github.com/klauspost/compress from v1.18.7 to v1.20.0.

Compression settings are static (read once at startup / dial time); they are not hot-reloadable.

Config

Param	Values	Default
grpc.client.compressionEnabled	bool	false
grpc.client.compressionAlgorithm	zstd / snappy / s2	zstd
grpc.client.compressionLevel	fastest / default / better / best	default
grpc.client.compressionCRC	bool	false

Compression applies to component-to-component gRPC traffic and remains opt-in via grpc.client.compressionEnabled.