Merge github.com:grpc/grpc into direct-calls

doc/interop-test-descriptions.md

src/core/ext/client_config/client_channel.c

src/core/ext/client_config/lb_policy.h

src/core/ext/lb_policy/grpclb/grpclb.c

src/core/ext/lb_policy/pick_first/pick_first.c

src/core/ext/lb_policy/round_robin/round_robin.c

src/core/ext/load_reporting/load_reporting.h

src/core/ext/load_reporting/load_reporting_filter.c

src/core/lib/transport/static_metadata.c

src/core/lib/transport/static_metadata.h

src/proto/grpc/testing/test.proto

test/core/end2end/fuzzers/hpack.dictionary

test/core/end2end/tests/load_reporting_hook.c

test/cpp/grpclb/grpclb_test.cc

test/cpp/interop/client.cc

test/cpp/interop/interop_client.cc

test/cpp/interop/interop_client.h

tools/codegen/core/gen_static_metadata.py