s2s compression support

[shikhar]

• client needs to send Accept-Encoding for the server to compress messages, and client can safely assume server supports zstd (preferred) as well as gzip https://s2.dev/docs/rest/records/overview#s2s-spec

• probably a good idea to skip compression for small messages (1 KiB is threshold tonic uses, so should be fair)

[infiniteregrets]

done in #217