gh-99344, gh-99379, gh-99382: Fix issues in substitution of ParamSpec and TypeVarTuple (GH-99412)

* Fix substitution of TypeVarTuple and ParamSpec together in user generics.

* Fix substitution of ParamSpec followed by TypeVarTuple in generic aliases.

* Check the number of arguments in substitution in user generics containing a
  TypeVarTuple and one or more TypeVar.