PAC as dotnet tool

[rajyraman]

I was reading though https://github.com/MicrosoftDocs/power-platform/issues/1835

Since PAC is being distributed through NuGet, it would be good if pac is released as a dotnet tool as well.

[tehcrashxor]

Latest release of PAC has also been released as a dotnet tool - Microsoft.PowerApps.CLI.Tool

Note that the VS Code extension that this repo covers is not yet updated to replace our packing of linux-x64 and osx-x64 versions, as the change came in too late for the release cutoff, but will likely be in next month's via #529