Update all GitHub actions to their current versions
Add a comment about why we need to stay on windows-2019
windows-latest doesn't have the older Windows SDK version we're targeting
Use startsWith in conditional tests, to reduce number of places to update in the future
Remove the manual install of .NET 5. We'll use the pre-installed version from the virtual environment.
Note, that we were installing 5.0.100, which is quite old now. Among other things, that was preventing the readme file from actually make it into the <readme> tag in the generated .nuspec file within the nuget package, as <PackageReadmeFile> tooling was added in 5.0.300.
windows-2019windows-latestdoesn't have the older Windows SDK version we're targetingstartsWithin conditional tests, to reduce number of places to update in the future<readme>tag in the generated .nuspec file within the nuget package, as<PackageReadmeFile>tooling was added in 5.0.300.skip-changelog