Currently, `push_error` and `push_warning` give themselve as the calling
function, which is not useful for debugging. I have altered these to use the
C stacktrace to get the name of the function that called them. This saves
having to turn these functions into macros, which would require recompiling
every single piece of code that uses them. I have also set it to, when debug
symbols are available, use them with `atos` (available on macOS) to find the
exact source file and line being called from. It should be possible to the same
thing on Linux using `addr2line`, but I don't have a Linux box handy to test
that. I am not sure how you would implement this in Windows.

I have tested this on macOS Sonoma 14.5 (23F79). It should work on any *nix
system. I am not sure about Windows.

Fixes godotengine#76770