Add compressed payload pass-through mode for SR Proxy

[banitag1]

Summary:
CONTEXT: Today the SR Proxy always decompresses inbound requests before
forwarding to the target service, then the channel layer recompresses on the
outbound side. For a pass-through proxy where routing metadata is in Rocket
RequestRpcMetadata (not inside the compressed payload), this decompress/
recompress cycle is pure CPU overhead.

WHAT: Add a pre-compressed payload pass-through mode that skips decompression
and recompression when the target service supports the same compression
algorithm. The feature is gated by the sr_proxy_enable_compression_passthrough
gflag (default false).

Thrift layer (Option E -- RpcOptions hint):

• Add preCompressedAlgorithm field to RpcOptions (C++ only, no IDL change)
• Add skipCompression param to packWithFds() across all PayloadSerializer
  strategies (Default, Checksum, CustomCompression) and the facade
• In sendThriftRequest(), check RpcOptions and set metadata.compression for
  the wire format while skipping actual compression in packWithFds()

SR Proxy layer:

• In processSerializedCompressedRequestWithMetadata(), when the gflag is
  enabled and the request is compressed, clone the compressed buffer directly
  into a SerializedRequest without decompressing
• Thread preCompressedAlgorithm through the full processing chain
  (processDecompressedRequest -> finishRequestProcessing -> channelProcessing)
• In the getRpcOptions lambda, set preCompressedAlgorithm on RpcOptions so
  the channel layer knows to skip compression

Reviewed By: kaczmarekmhl

Differential Revision: D100276926

[meta-codesync]

@banitag1 has exported this pull request. If you are a Meta employee, you can view the originating Diff in D100276926.