fix: add updated signature for getenv

[msbit]

Add the following signature for getenv:

 getenv(?string $name = null, bool $local_only = false): string|array|false

to the function map (specifically for PHP 8 and above). This replaces all existing signatures, and should fix 13065.

[msbit]

@ondrejmirtes let me know if this is what you were expecting. It shows no error for the following:

<?php

getenv();
getenv(null);
getenv('TERM');
getenv(null, false);
getenv(null, true);
getenv('TERM', false);
getenv('TERM', true);

[msbit]

@ondrejmirtes I'm not sure about the interactions of optional arguments (name=) to allow this to replicate the no-argument override in the base function map. Do you have any advice?

[VincentLanglet]

@msbit Fixed by #4007