* Remove obsolete targets, properties, and scripts
* Replace IsProductComponent with IsShipping
* Undo bad merge to version.props
* Update documentation, and put workarounds into a common file
* Replace usages of RepositoryRoot with RepoRoot
* Remove API baselines
* Remove unnecessary restore feeds and split workarounds into two files
* Enable PR checks on all branches, and disable autocancel
.NET Core 2.0 reached EOL last year. This removes multi-targeting our test projects and test assets to only use .NET Core 2.1 and .NET Framework 4.6.1.
Addresses #571
Using `TaskCreationOptions.LongRunning` creates a dedicated thread, but
it's released on the first await. Using Task.Run uses the thread pool
instead
Nate McMaster
Ryan Brandenburg
Nate McMaster
John Luo
Andrew Lock
Pavel Krymets