stream_filter_append & stream_filter_prepend use mixed instead of array

[ildyria]

https://www.php.net/manual/en/function.stream-filter-append.php
Defines stream_filter_append as :

stream_filter_append(
    resource $stream,
    string $filtername,
    int $read_write = ?,
    [mixed](https://www.php.net/manual/en/language.types.declarations.php#language.types.declarations.mixed) $params = ?
): resource

This PR aims to fix the inconsistency as here $params is defined as array.

Also updates https://www.php.net/manual/en/function.stream-filter-prepend.php

[Kharhamel]

You cannot directly update the generated files because the change will be lost the next time we will regenerate them. You need to update the generator instead.

To solve this, the simple solution is to edit this file: https://github.com/thecodingmachine/safe/blob/master/generator/config/CustomPhpStanFunctionMap.php
To make stream_filter_append return the type you want

[ildyria]

@Kharhamel I updated as you advised.

[Kharhamel]

Thank you for the MR. I will deploy this shortly