Log Message:
grpc: updated to 1.22.0

Release v1.22.0

Core
building upb as part of cmake build is not necessary (for v1.22.x).
Convert TraceFlags in the hot path to DebugTraceFlags.
Fix a bug where POST_RECV_MESSAGE was not being triggered.
Adjust the order of IOMgr timer initialization and comment of grpc_timer::heap_index.

C++
use bazel wrapper for "bazel" invocations in grpc workspace.
Add method to validate service config json.
Update comment on ssl hostname override.
Rename root certificate bundle in gRPC-C++ pod.