Arcade SDK: consider removing -deploy and DeployProjectOutput

[tmat]

Repos can pass /p:DeployExtension=false or set the property in VSIX projects explicitly.

[jcagme]

I see that DeployProjectOutput is only defined here https://github.com/dotnet/arcade/blob/master/src/Microsoft.DotNet.Arcade.Sdk/tools/Imports.targets#L15. What's the benefit of removing it?