Mark type-check macro expansions as generated - #15888

Since %_{} patterns became precise (#15635), the type-check macros leak warnings from their own expansion whenever the argument type is statically known. Calling is_struct/1 on a struct:

defmodule Foo do
  def uri?(%URI{} = uri), do: is_struct(uri)
end

$ elixirc foo.ex
warning: the following clause cannot match because the previous clauses already matched all possible values:

    _ ->

it attempts to match on the result of:

    uri

which has the already matched type:

    %URI{...}

The _ -> false clause belongs to the macro expansion, so the warning points at code the caller never wrote. The same happens with is_exception/1 and is_non_struct_map/1, and in rescue clauses (rescue x -> ... is_exception(x)); compiling the test suite on main emits this warning for the doctest of try/rescue x -> ... in Kernel.SpecialForms. It also fires in the other direction: x = %{}; is_struct(x) warns that the %_{} clause will never match, and e = %ArgumentError{}; is_exception(e, ArgumentError) hits is_exception/2 through the pinned name.

is_struct/2 already wraps its whole expression expansion in quote generated: true, which is why it never triggers these warnings. This does the same for the remaining macros. Guards and match contexts are untouched.