[DI] Autodiscover AnnotationToAttributeMapper via mutually exclusive candidates

[TomasVotruba]

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

AnnotationToAttributeMapper matched by first isCandidate() in registration order. The one order-sensitive overlap: StringAnnotationToAttributeMapper::isCandidate() returned is_string($value) — a superset of ClassConstFetchAnnotationToAttributeMapper (is_string && contains '::' && not quoted). A value like Foo::BAR matched both, and the curated order let the class-const mapper win. autodiscover() filesystem order would not honor that.

Rather than a consumer change, this makes the two candidates mutually exclusive, so match order is irrelevant:

publicfunctionisCandidate(mixed$value): bool
{
if (! is_string($value)) {
returnfalse;
}
// an unquoted "Class::CONST" reference is handled by the class const fetch mapperreturn ! str_contains($value, '::') || str_starts_with($value, '"');
}

ANNOTATION_TO_ATTRIBUTE_MAPPER_CLASSES collapses to one autodiscover() call.

Verified the two mappers no longer both claim any value (behavior identical to the old first-match order):

value	class-const mapper	string mapper
Foo::BAR	yes	no
plain	no	yes
"quoted::x"	no	yes

Interface added to the class-leak skip list.