@noscope macro / changing try scoping rules.

[c42f]

As argued in JuliaLang/julia#39217, it would be nice to be able to opt out of scoping in some cases, in particular try ... catch .. end. Triage liked the @noscope macro: JuliaLang/julia#39217 (comment) and maybe we can implement this in the future.

This may be a 2.0 language feature (see JuliaLang/julia#48434). Though I think we could do this in a 1.x Julia Edition since we can detect any semantic changes using static analysis in lowering and in principle write a refactoring pass (see JuliaLang/julia#54903)