fix: crashes in ZTS build because of overloaded functions

[dunglas]

Closes dunglas/frankenphp#563, closes api-platform/api-platform#2670, closes dunglas/symfony-docker#534, closes https://bugs.xdebug.org/view.php?id=2216, and likely many other random bugs and crashes with ZTS builds.

Rationale:

The function table is (as expected) a different copy for each thread, but each copy points to the same underlying zend_functions, and as we modify them in concurrent threads,, we have a thread safety issue.

In xdebug_base_overloaded_functions_setup, if a thread changes orig->internal_function.handler, then a concurrent thread reads orig->internal_function.handler and stores its value in XG_BASE(orig_error_reporting_func), XG_BASE(orig_error_reporting_func) points to the Xdebug version, instead of to the PHP internal function, and when XG_BASE(orig_error_reporting_func) is called... we get infinite recursion.

This patch moves function overloading in MINIT, as it looks expected: https://www.phpinternalsbook.com/php7/extensions_design/hooks.html#overwriting-an-internal-function

This also allows to simplify the code.

I tested it on Linux, and it fixes the crashes as expected.

[derickr]

This looks good, but can you:

• squash the commits
• target the PR to the xdebug_3_3 branch?
• rephrase your commit message according to the contributing guidelines (https://github.com/xdebug/xdebug/blob/master/CONTRIBUTING.rst#branches) (don't worry about renaming your branch, and feel free to co-opt issue)