[llvm] [GitHub] Add workflows to manage merging of PRs from authors without commit access (PR #124910)

[David Spickett via llvm-commits]

DavidSpickett wrote:

As noted in the PR description, this "state machine" is somewhat fragile and will always have some weird scenarios. But I don't say that to excuse that, please come up with as many weird situations as you can think of to trip this up!

That way we can at least look at each one and weigh the complexity of handling it vs. the impact of it happening.

https://github.com/llvm/llvm-project/pull/124910