Enable unpack/repack of .rpm containers

[mmitche]

.rpm files contain signable binaries within. Enable unpack and repack of these containers.

T-Shirt Size: S

[dotnet-issue-labeler]

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[jkoritzinsky]

Depends on #15143

[ellahathaway]

@jkoritzinsky - same comment as #14436 (comment). Can you help me give a tshirt size estimate for this work?

[jkoritzinsky]

I think this one would be T-Shirt Size: S

There's a little more work than the deb case as you need to finish signing all of the files first before you re-assemble the rpm, and you need to reassemble the cpio archive first as well (and that's a little annoying).

[jkoritzinsky]

My size might be off by 1 if there's additional PRs for other validation work or hooking up/enablement than just the feature work in SignTool (ie if there'd be multiple PRs across multiple repos like for the pkg work).

[ellahathaway]

Awesome, thanks. I'll mark it as size S for now and we can reevaluate once the issue is in progress.