support Directory.Build.props at top level (where .git is) automatically

[4xmg]

Support for .targets was added 2021.
But MS current recommendation is to place in Directory.Build.props, which .csproj auto-include and CAN override.

1. .props should be supported, or better yet, the code (which is a one line to test for .csproj/.targets) should see if the file is XML with tag.
2. Directory.Build.props, if exist at top level and 'dotnet version' run at top level (where .git is) should be used automatically (no -f required)

more info on Directory.Build.props:
https://learn.microsoft.com/en-us/visualstudio/msbuild/customize-by-directory?view=vs-2022