Add UnusedVariableNames missing checks

[Wigny]

While solving ours {Credo.Check.Consistency.UnusedVariableNames, [force: :meaningful]} check issues, I noticed that many cases were not being caught by the check, such as:

# match in tuples
{:ok, _} = fun1()

# match inside `with`
with {:ok, _} <- fun1(), do: :ok

# match in lists
def fun2([_ | _]) do
end

# for macros 
defmacro __using__(_) do
end

This MR adds the missing checks I could notice, so feel free to add/point any other cases we could still be missing.