Allow infix () and {} to call "call" on the left-hand side.

- Allow this for both argument lists and block arguments.

- Tweak precedence to make "." higher than infix "{}" to avoid a
  class body being parsed as the superclass clause's block argument.

- Convert all uses of ".call" to use this. (There was not a single
  case in the repo that ran into the getter ambiguity.)

test/language/module_variable/assignment.wren

@@ -14,5 +14,5 @@ System.print(variable) // expect: method
 
 Fn.new {
   variable = "fn"
-}.call()
+}()
 System.print(variable) // expect: fn