Remove contrib from Stackdriver

[mic-max]

Towards #196

Note: This does not change the directory structure at all or the test project name or the namespaces.

[codecov]

Codecov Report

Merging #223 (3869461) into main (51128b0) will not change coverage.
The diff coverage is n/a.

❗ Current head 3869461 differs from pull request most recent head db2860c. Consider uploading reports for the commit db2860c to get more accurate results

@@           Coverage Diff           @@
##             main     #223   +/-   ##
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  Coverage   79.14%   79.14%           
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  Files          97       97           
  Lines        2498     2498           
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  Hits         1977     1977           
  Misses        521      521           

[SergeyKanzhelev]

Can you please add a note into the changelog https://github.com/open-telemetry/opentelemetry-dotnet-contrib/blob/main/src/OpenTelemetry.Contrib.Exporter.Stackdriver/CHANGELOG.md

[cijothomas]

Lets be a bit more specific here:
The nuget package will named `OpenTelemetry.Exporter.Stackdrive" going forward. Add link-to-new one (It'll be a deadlink now, but once we publish it'll be fixed). The old versions can still be found in nuget.org/link-to-old-package.

[cijothomas]

^^ something like this which advices the users about the impact of this on them, and how to manage the impact.