Do not typehint DNF union types

[scyzoryck]

Q	A
Bug fix?	yes
New feature?	no
Doc updated	no
BC breaks?	no
Deprecations?	no
Tests pass?	yes
Fixed tickets	#1584
License	MIT

Tests coverage based on: https://wiki.php.net/rfc/dnf_types

@goetas I need your opinion on that:

1. Current implementation skips any cases of Disjunctive Normal Form Types.
2. Alternative solution would be to skip only Intersection types, so (A&B)|D could be resolved into D, when (A&B)|C|D into union<C,D>

Looking at the use cases like ArrayCollections from Doctrine I guess second option might be more intuitive for users, when first safer as it brings back behavior from prev lib versions. 🤔

[goetas]

I'm fine with not supporting such expressions.

I really hope no one uses them! :D