[WIP] FEATURE: Rake task to uninstall theme (PR #10138)

This is a work-in-progress PR to allowing uninstalling a theme or a theme component via rake.


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@chandandi If the only use case for this is updating a theme (by removing and re-installing), I would rather close this PR, as I fixed updating.

Thanks @markvanlan for the fix! I don’t see an option to close the PR. Could you do that if you have the access.