[DI] Autodiscover TypeMapper via most-specific match

[TomasVotruba]

One of three parallel experiments removing order-sensitive registerTagged() collections in favor of autodiscover().

TypeMapper could not be autodiscovered before because PHPStanStaticTypeMapper matched mappers by first instanceof match in registration order — a mapper for a child type (ConstantArrayType) had to be registered before the mapper for its parent (ArrayType), or the parent would always win. autodiscover() uses filesystem order, which does not honor that.

This removes the order dependency instead of encoding it: the consumer now picks the most specific matching mapper (deepest in the type hierarchy), so registration order no longer matters.

privatefunctionmatchTypeMapper(Type$type): ?TypeMapperInterface
{
$matchedTypeMapper = null;
$matchedNodeClass = null;
foreach ($this->typeMappersas$typeMapper) {
foreach ($typeMapper->getNodeClasses() as$nodeClass) {
if (! $typeinstanceof$nodeClass) {
continue;
}
if ($matchedNodeClass === null || is_a($nodeClass, $matchedNodeClass, true)) {
$matchedNodeClass = $nodeClass;
$matchedTypeMapper = $typeMapper;
}
}
}
return$matchedTypeMapper;
}

With that, TYPE_MAPPER_CLASSES (29 entries) drops to a single autodiscover() call, and the now-obsolete TypeMapperOrderTest (which guarded the old registration-order invariant) is removed.

Verified directly against the real mappers:

Type	Resolves to
ConstantArrayType	ArrayShapeNode (specific, not the generic array mapper)
ClassStringType	class-string (not the StringType mapper)
ObjectType	\Foo (not the TypeWithClassName mapper)

Interface added to the class-leak skip list (implementors are now discovered, not referenced).