profiler: update profiler to use auto-generated client libraries for cloudprofiler.

**Is your feature request related to a problem? Please describe.**
Making the profiler agent use the auto-generated client-libraries would help reduce maintenance burden and avoid potential protobuf registration conflicts if the agent is used in conjunction with client library in the same application.

**Describe the solution you'd like**
The profiler go agent should use the auto-generated clients to access cloud-profiler APIs.