Merge pull request dotnet/coreclr#7510 from kouvel/ApiThread

Expose some members of the Thread class

Commit migrated from https://github.com/dotnet/coreclr/commit/1e37d9f35f757d77345fb75929f0472e9bb54c30

diff --cc src/coreclr/src/mscorlib/model.xml
Simple merge

diff --cc src/coreclr/src/mscorlib/mscorlib.shared.sources.props
Simple merge

diff --cc src/coreclr/src/mscorlib/ref/mscorlib.cs
Simple merge