Refine usage of Central Package Management

[pellared]

After seeing PRs like this #2054 I think that too much has been moved to Central Package Management.

I think that the instrumented library version should be declared only in csproj.

The purpose of the PR was to make it easier for upgrading versions, especially for shared dependencies used in multiple places. The opentelemetry-dotnet repo centralizes almost all versions because most of them are shared. However, the same might not apply to this repo seeing recent PRs.

I took a look at the recent dependabot PRs. Most of them are either in CommonExcludedAssets.props (9) or in tests/Directory.Packages.props (5).

The packages in tests/Directory.Packages.props file aren't shared much (the csproj files are in test/test-applications/integrations/). I can put them back.

Regarding CommonExcludedAssets.props, these seems like to be excluding packages of old versions not expected to be upgraded as new versions come by. I didn't manage to figure out how they got skipped by dependabot before. Shall I put the versions back to CommonExcludedAssets.props file as well?

Originally posted by @xiang17 in #2004 (comment)

[pellared]

This is no longer an issue after #2230