Contribution to the .NET OpenTelemetry client.

Clean up package version definitions using Directory.Packages.props.

I'm creating a root Directory.Packages.props and others in specific folders to override some of the root package versions based on what I found in Common.props and Common.nonprod.props:

Some properties are used in power shell scripts, like MicrosoftCodeCoveragePkgVer and OTelPreviousStableVer, so I'm keeping them in Common.props;

Other packages like SerilogPkgVer and SystemCollectionsImmutablePkgVer are not being used in any .cspjoj so I deleted their reference from Common.props.

CONTRIBUTING guidelines followed (nullable enabled, static analysis, etc.)

Unit tests added/updated

Appropriate CHANGELOG.md files updated for non-trivial changes

Changes in public API reviewed (if applicable)

The following error was thrown after central package management because opentelemetry.net is using more than one package source:

error NU1507: Warning As Error: There are 2 package sources defined in your configuration. When using central package management, please map your package sources with package source mapping (https://aka.ms/nuget-package-source-mapping) or specify a single package source. The following sources are defined: NuGet, .Net Core Tools

There are two solutions:

To ignore the warning (as error) with <NoWarn>$(NoWarn);NU1507</NoWarn>. I don't think this is the best option;

Enable package source mapping.

As I'm choosing to follow the second approach, I need to know what packages (or package name pattern) should be restored by the .Net Core Tools source.