Provide a way to start off with a large set of files in input files - for instance, the entirety of the git repo the test is running in

[richardpark-msft]

For people developing skills that are within the repo they run in (ie, azure-sdk-for-rust), the skills will use files from 'eng', or will leverage other code or packages within the repo for examples.

The current mechanism for setting up inputs, per task, only accepts files. We could do a few things here:

• We could provide an easy 'bool' that says "use a git worktree". This would be a pretty cheap way of getting a copy of the repo, and it's a simple "true/false" style option.
• Provide ways for users to specify folders, not just files. Currently the ResourceRef is just a file list, but we could provide some shorthand so larger parts of fixtures could be copied, etc...

CC: @LarryOsterman