Add array_chunk() throw type extension - #6524

PhpStorm stubs now declare @throws \ValueError on array_chunk(), so every call became an explicit throw point.

array_chunk() throws ValueError (Argument #2 ($length) must be greater than 0) only when $length is less than 1. This happens even for an empty array. It is the same on PHP 8.0–8.5, and PHP 7 only warns.

The extension returns VoidType when the analysed PHP version is below 8.0, or when the native type of $length is a subtype of int<1, max>. Otherwise it keeps the ValueError. That covers array_chunk($a, 0), a native int $length, and a PHPDoc-only positive-int. A native narrowing like if ($length > 0) removes it.

Tests are in CatchWithUnthrownExceptionRuleTest, with separate expectations for PHP 8.0+ and for PHP < 8.0, where every catch is dead. Both fail without the extension; the < 8.0 expectations were verified locally on PHP 7.4.

The PRs for array_chunk(), get_class(), hash(), array_fill() and unserialize() are all based on 2.2.x. They add their test methods at different places in CatchWithUnthrownExceptionRuleTest, so they merge cleanly in any order (checked).

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