[CodingStyle] Keep trait use adaptations in SeparateMultiUseImportsRector

[calebdw]

SeparateMultiUseImportsRector only carries Alias adaptations onto the split
statements, so every other adaptation is dropped together with the grouped
statement it sat on.

The one that hurts is insteadof:

class SomeClass
{
    use A, B {
        A::collide insteadof B;
    }
}

becomes

class SomeClass
{
    use A;
    use B;
}

Nothing is left to resolve the conflict, so the class no longer loads:

Trait method A::collide has not been applied as SomeClass::collide, because of collision with B::collide

An Alias that names no trait (exec as renamed;) is dropped just as silently,
taking the aliased method with it.

Fix

A Precedence adaptation now follows the trait it names, the same way an alias
already did — PHP accepts the adaptation on the winning trait's own statement:

use A {
    A::collide insteadof B;
}
use B;

Two kinds cannot follow a single trait, and for those the statement is left
alone rather than rewritten:

• an adaptation naming no trait applies to all of the used traits
• an adaptation naming a trait used in a different statement belongs to none
  of the ones being split, e.g. use A; use B, C { A::exec insteadof B; }

Tests

• with_trait_use_precedence — the insteadof case above
• skip_unqualified_trait_use_adaptation — adaptation naming no trait
• skip_trait_use_adaptation_of_other_statement — adaptation naming a trait from another statement

The existing alias fixtures are unchanged.

[TomasVotruba]

LGTM, thanks