Delete FatalError.ReportIfNonFatalAndCatchUnlessCanceled

[jasonmalinowski]

#58094 introduced this method as a shim for several places in the compiler that needed that specific behavior. It was agreed that we really don't want that behavior, but it was prudent to not change things for 17.1 given our relative lateness in the cycle. We want to rip it out immediately at the start of 17.2, so if there are any bugs still being masked we can have sufficient time to react to them.

The last commit in the PR details the precise set of steps we want to do to undo it.

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.