Deprecate erlang:exit/2 and erlang:exit/3

[richcarl]

This is a followup based on #10801 and intended for OTP 30.

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[mikpe]

Why? What problem does this solve?

[richcarl]

Why? What problem does this solve?

Apart from the small detail that exit/2 ignores signals sent by a process to itself (probably rare that this happens, but if it does, it could be quite confusing), the main thing is that exit/1 and exit/2 do very different things, one on the exception level and the other on the signal level. When reading code, it's very easy to miss that what you thought was a simple exit/1 was in fact an exit/2 or vice versa - in particular if they occur in the same module. (I've seen cases with exactly one exit/2 among a bunch of exit/1.)

So I think there is a point, for maintainability, to have a warning that steers people towards using exit_signal/2 instead. Especially if documentation and training material moves on to using the new name, calls to exit/2 will become even more obscure.