New Features

balancer/ringhash: move LB policy from xds/internal to exported path to facilitate use without xds (#8249)
xds: enable least request LB policy by default. It can be disabled by setting GRPC_EXPERIMENTAL_ENABLE_LEAST_REQUEST=false in your environment. (#8253)
grpc: add a CallAuthority Call Option that can be used to overwrite the http :authority header on per-RPC basis. (#8068)
stats/opentelemetry: add trace event for name resolution delay. (#8074)
health: added List method to gRPC Health service. (#8155)
- Special Thanks: @marcoshuck
ringhash: implement features from gRFC A76. (#8159)
xds: add functionality to support SPIFFE Bundle Maps as roots of trust in XDS which can be enabled by setting GRPC_EXPERIMENTAL_XDS_MTLS_SPIFFE=true. (#8167, #8180, #8229, #8343)

Bug Fixes

xds: locality ID metric label is changed to make it consistent with gRFC A78. (#8256)
client: fail RPCs on the client when using extremely short contexts that expire before the grpc-timeout header is created. (#8312)
server: non-positive grpc-timeout header values are now rejected. This is consistent with the gRPC protocol spec. (#8290)
- Special Thanks: @evanj
xds: fix reported error string when LRS load reporting interval is invalid. (#8224)
- Special Thanks: @alingse

credentials/alts: improve read performance by optimizing buffer copies and allocations. (#8271)
server: improve performance of RPC handling by avoid a status proto copy (#8282)
- Special Thanks: @evanj

examples/features/opentelemetry: modify example to demonstrate tracing using OpenTelemtry plugin. (#8056)