Support a --file option for dsc config * commands

[michaeltlombardi]

Summary of the new feature / enhancement

As a user working with DSC Configuration documents, I want to be able to specify the path to a configuration document saved as a file so that I can point DSC to saved files instead of always piping/redirecting the contents of a document to DSC.

For example:

dsc config test --file ./app.dsc.config.yaml
dsc config test -f ../security/baseline.dsc.config.yaml

Proposed technical implementation details (optional)

No response

[SteveL-MSFT]

I'll add both -input and -inputFile parameters. These will be global, so it'll be before the subcommand.