collector: use buildinfo to make user agent

[braydonk]

redo of #1018

This PR adjusts the NewGoogleCloud*Exporter functions to take a
component.BuildInfo, and to format that build info into the UserAgent
instead of defaulting to opentelemetry-collector-contrib.

[codecov]

Codecov Report

Attention: Patch coverage is 82.45614% with 10 lines in your changes missing coverage. Please review.

Project coverage is 64.31%. Comparing base (4caace7) to head (13f8e5a).
Report is 125 commits behind head on main.

Files with missing lines	Patch %	Lines
exporter/collector/config.go	78.57%	3 Missing ⚠️
...llector/integrationtest/cmd/recordfixtures/main.go	0.00%	3 Missing ⚠️
exporter/collector/logs.go	0.00%	3 Missing ⚠️
...er/collector/integrationtest/protos/fixtures.pb.go	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1022      +/-   ##
==========================================
+ Coverage   61.03%   64.31%   +3.28%     
==========================================
  Files          56       58       +2     
  Lines        5903     6048     +145     
==========================================
+ Hits         3603     3890     +287     
+ Misses       2143     1999     -144     
- Partials      157      159       +2     

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[braydonk]

Opened a draft PR with the changes I made and tested with go replace of this branch. When the new release is cut here, I will make this PR point to the release and open it for review.

open-telemetry/opentelemetry-collector-contrib#38116