11107: Fix generic type substitution in impl trait with assoc type r=pnevyk a=pnevyk
Fixes#11045
The path transform now detects if a type parameter that is being substituted has an associated type. In that case it is necessary (or safe in general case) to fully qualify the substitution with a trait which the associated type belongs to.
This PR also fixes the previous wrong behavior of the substitution that could create an invalid tree `PATH_TYPE -> PATH_TYPE -> ...`.
Co-authored-by: Petr Nevyhoštěný <petr.nevyhosteny@gmail.com>
c17db9fa53