Switch the native function calls to `thecodingmachine/safe`

[oliverklee]

This package provides versions of native PHP functions that throw an exception in case of an error instead of returning false. We also should use the corresponding set of PHPStan rules to make sure we use the safe version of functions.

Due to us supporting PHP 7.x as well, we need to use lower versions of these packages:

• thecodingmachine/safe 1.3.3
• thecodingmachine/phpstan-safe-rule 1.2.0 || 1.4.0 (to allow PHPStan 2)