New rust-lang/rust workflow based on patches

[roblabla]

Fixes #583

[roblabla]

This needs a few improvements before I'm confident with it. Currently, setup-rust will silently do nothing if the rust folder already exists. That's fairly conservative, which is a good property, but there is one case that I'd like to support before going forward: The user has done no changes to their rust repo, and the patches got updated. In this case, we should update their rust repo to the latest patches.

The other case to think about: The user has changes to their rust repo, and the patches got updated. In this case, the ideal thing to do would be to print a warning to the user telling them they need to somehow merge their patches with upstream's.

The difficulty here is that it's hard to detect if the patches got updated, especially since the user might cause a patch to change by amending an existing commit. We can probably detect unchanged patches through authorid shenanigans.

[sagiegurari]

@roblabla i wonder if instead of dependencies = ["install-xargo", "setup-rust"] everywhere, you might want to do either

• have an init task that invokes those 2
• have 1 task that everyone depends on, and that task depends on those 2.

both will enable you to make that basic dependencies list grow without having to change all tasks each time (ya, i know its probably rare, but still).

by the way, happy to see that duckscript was able to provide you of a cross platform scripting solution :) it looks great. thanks for the bug reports.