message: Introduce protobuf fields to support monitoring feature on cloud.
diff: @@ -11,6 +11,9 @@ service TPUProfiler {
  // Starts a profiling session, blocks until it completes, and returns data.
  rpc Profile(ProfileRequest) returns (ProfileResponse) {
  }
  + // Collects profiling data and returns user-friendly metrics.
  + rpc Monitor(MonitorRequest) returns (MonitorResponse) {
  + }
  }
  message ProfileOptions {
  @@ -104,3 +107,26 @@ message ProfileResponse {
  // next-field: 8
  }
  +
  +message MonitorRequest {
  + // Duration for which to profile between each update.
  + uint64 duration_ms = 1;
  +
  + // Indicates the level at which we want to monitor. Currently, two levels are
  + // supported:
  + // Level 1: An ultra lightweight mode that captures only some utilization
  + // metrics.
  + // Level 2: More verbose than level 1. Collects utilization metrics, device
  + // information, step time information, etc. Do not use this option if the TPU
  + // host is being very heavily used.
  + int32 monitoring_level = 2;
  +
  + // next-field: 3
  +}
  +
  +message MonitorResponse {
  + // Properly formatted string data that can be directly returned back to user.
  + string data = 1;
  +
  + // next-field: 2
  +}
  