Restore stacktrace scrubing in fallback REPL.

[BioTurboNick]

Fixes #59223 by adding intermediary function names to use the same __repl_entry prefix.

[Keno]

LGTM, but needs a test

[BioTurboNick]

Added tests. Let me know though if my assumption about Meta.lower not throwing exceptions (in a way that can be mocked here) is accurate. I looked to see if there was a way and there didn't seem to be.

[BioTurboNick]

A slight wrinkle here is that the eval frame will still show up in stacktraces. REPL.jl gets around that by calling a C function to do the eval, which are hidden normally. But that may not be worth trying to achieve?

[Keno]

Is it really that important? The fallback REPL isn't really supposed to be used regularly.