lang: ast: The res and edge names should not use exclusives

This removes the exclusive from the res names and edge names. We now
require that the names should be lists of strings, however they can
still be single strings if that can be determined statically.
Programmers should explicitly wrap their variables in a string by
interpolation to force this, or in square brackets to force a list. The
former is generally preferable because it generates a small function
graph since it doesn't need to build a list.

lang/interpret_test/TestAstFunc1/simple-lambda2.txtar

@@ -9,14 +9,16 @@ $answer = func() {
 $out1 = $answer()
 $out2 = $answer()
 
-test $out1 + $out2 {}
+test [$out1 + $out2,] {}
 -- OUTPUT --
 Edge: FuncValue -> call # fn
 Edge: FuncValue -> call # fn
 Edge: FuncValue -> call # fn
+Edge: call -> composite # 0
 Vertex: FuncValue
 Vertex: FuncValue
 Vertex: call
 Vertex: call
 Vertex: call
+Vertex: composite
 Vertex: const