librustc: Ensure that proc upvars have static lifetime.

Since procs do not have lifetime bounds, we must do this to maintain
safety.

This can break code that incorrectly captured references in procedure
types. Change such code to not do this, perhaps with a trait object
instead.

Closes #14036.

[breaking-change]

r? @alexcrichton
I would personally rather this have the two procedures to using closures instead. It will involve an option dance here and there, however.