Skip the generic object type search on types without classes

[Kocal]

GenericObjectTypeCheck::getGenericTypes() walks the whole PHPDoc type with TypeTraverser::map() to collect every GenericObjectType and GenericStaticType. It now returns early when the type references no class (getReferencedClasses() === []) and hasTemplateOrLateResolvableType() is false. A generic object type always references its class, so the first check alone would miss nothing from that side. The second condition covers what getReferencedClasses() does not see: a template type's default (e.g. @template T = Box<int, string, bool>, then @param T) and late-resolvable types; both make hasTemplateOrLateResolvableType() true. When the traversal does run, nothing changes: it still collects every occurrence with map(), so this is independent from #6652.

This matters on the symfony/ux-css array shape (847 keys, 144 of them a nested shape alias, no class anywhere), where the traversal was visiting the shared nested shape once per offset using it. With #6671, both getReferencedClasses() and hasTemplateOrLateResolvableType() are memoized on ConstantArrayType, so the check is nearly free there.

IncompatiblePhpDocTypeRuleTest::testGenericObjectTypeInTemplateDefault covers the template default case. It passes before and after this change, and fails if the guard only checks getReferencedClasses().

As a safety check, I temporarily logged every traversal that found a generic type while the guard would have skipped it: 0 cases out of 1623 traversals that found one, over the full test suite and PHPStan's self-analysis.

Numbers from https://github.com/Kocal/sf-ux-css-phpstan-reproducer with phpstan-nested.neon, --debug, 6 interleaved runs, first discarded:

Scenario	Before	After
2.3.x without turbo	12.98-13.21 s	12.79-12.85 s
2.3.x + #6652 + #6671 + #6672 without turbo	2.14-2.26 s	1.66-1.71 s
2.3.x with turbo	5.90-6.07 s	5.65-5.69 s

On ordinary code the guard costs nothing measurable: PHPStan analysing its own src/Type (about 28 s) calls it 683 times, the guard costs about 1 ms in total and skips about 0.75 ms of traversal.

make tests passes with and without the turbo extension, make phpstan and make cs pass.

Refs phpstan/phpstan#15348