Pprofile marshal/unmarshalling and gRPC implementations

[dmathieu]

Description

This adds pprofile marshaling/unmarshaling, as well as the gRPC implementation, so we can start setup the OTLP receivers and exporters.

[codecov]

Codecov Report

Attention: Patch coverage is 92.73504% with 34 lines in your changes missing coverage. Please review.

Project coverage is 92.24%. Comparing base (46d0f73) to head (42bdfb1).
Report is 12 commits behind head on main.

Files with missing lines	Patch %	Lines
pdata/pprofile/pprofileotlp/request.go	62.06%	9 Missing and 2 partials ⚠️
pdata/pprofile/pprofileotlp/response.go	76.92%	9 Missing ⚠️
pdata/pprofile/json.go	97.56%	8 Missing ⚠️
pdata/pprofile/pprofileotlp/grpc.go	78.94%	4 Missing ⚠️
pdata/internal/data/profileid.go	92.59%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##             main   #11048    +/-   ##
========================================
  Coverage   92.23%   92.24%            
========================================
  Files         406      412     +6     
  Lines       19101    19554   +453     
========================================
+ Hits        17618    18037   +419     
- Misses       1123     1154    +31     
- Partials      360      363     +3     

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[mx-psi]

Since I can't see any users of this API according to this search https://github.com/search?q=-repo%3Aopen-telemetry%2Fopentelemetry-collector++go.opentelemetry.io%2Fcollector%2Fpdata%2Fpprofile+language%3AGo+-is%3Afork&type=code I think we can do this change in one step.