New Features

metadata: stabilize ValueFromIncomingContext (#7368)
- Special Thanks: @KarthikReddyPuli
client: stabilize the WaitForStateChange and GetState methods, which were previously experimental. (#7425)
xds: Implement ADS flow control mechanism (#7458)
- See grpc/grpc#34099 for context.
balancer/rls: Add metrics for data cache and picker internals (#7484, #7495)
xds: LRS load reports now include the total_issued_requests field. (#7544)

Bug Fixes

grpc: Clients now return status code INTERNAL instead of UNIMPLEMENTED when the server uses an unsupported compressor. This is consistent with the gRPC compression spec. (#7461)
- Special Thanks: @Gayathri625
transport: Fix a bug which could result in writes busy looping when the underlying conn.Write returns errors (#7394)
- Special Thanks: @veshij
client: fix race that could lead to orphaned connections and associated resources. (#7390)
xds: use locality from the connected address for load reporting with pick_first (#7378)
- without this fix, if a priority contains multiple localities with pick_first, load was reported for the wrong locality
client: prevent hanging during ClientConn.Close() when the network is unreachable (#7540)

transport: double buffering is avoided when using an http connect proxy and the target server waits for client to send the first message. (#7424)
codec: Implement a new Codec which uses buffer recycling for encoded message (#7356)
- introduce a mem package to facilitate buffer reuse (#7432)
- Special Thanks: @PapaCharlie