GitHub actions to remove outdated patches/revisions

[sifferman]

Hello!

It is my opinion that this project is most helpful when it delivers as close to the latest unmodified version as possible. Many untracked patches/revision freezes will make that goal difficult.

#89 and #100 remove outdated patches for Verilator. I've noticed there are dozens of patches across many different tools, as well as many tool versions that are frozen at a specific revision. It seems fairly challenging to keep track of outdated patches/revision freezes.

Would it be possible to add some automatic testing on whether a patch/revision freeze is still necessary? I imagine this can be achieved with attaching a test to every patch:

1. Every patched project should be built twice: once with the patch, and once without
2. A test is run on both the patched and unpatched versions

	Unpatched Passes	Unpatched Fails
Patched Passes	ALERT "Patch no longer needed"	(no alert, patch working as intended)
Patched Fails	ALERT "Patch breaks compatibility"	ALERT "Patch insufficient"

I bring this up, because I see that Icarus' revision was just frozen d22858d, although it gets frequent updates that are very helpful for users. I would like to see some automatic testing for when the revision can be unfrozen.

Thanks!