Allow to define custom taint types classes

[ohader]

Currently custom taint types are plain strings like "anything" and wrapped in class generic TaintedCustom. To add more semantics and better taint graph handling, those types should be regular classes like AnythingTaint and optionally be "connected" to existing groups like TaintKindGroup::ALL_INPUT. In case no specific class is defined, it still falls back to current TaintedCustom behavior.

Example: https://psalm.dev/r/b0cf89613b

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/b0cf89613b

<?php // --taint-analysis
/**
 * @psalm-taint-sink anything $value
 */
function any($value) {}
/**
 * @psalm-taint-source anything
 */
function getData(): string {}

$inject = getData();
any($inject);

Psalm output (using commit aec0edc):

ERROR: TaintedCustom - 5:14 - Detected tainted anything