[builtins] Unify the various versions of [[Call]] with a Call builtin.

test/mjsunit/harmony/proxies-function.js

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 102 matching lines @@
   assertSame(isStrict ? null : global_object, receiver)
   receiver = 333
   assertEquals(42, %Apply(f, o, [11, 31], 0, 2))
   assertSame(o, receiver)
   receiver = 333
   assertEquals(42, %Apply(f, null, [11, 31], 0, 2))
   assertSame(isStrict ? null : global_object, receiver)
   receiver = 333
   assertEquals(42, %_CallFunction(o, 11, 31, f))
   assertSame(o, receiver)
-  receiver = 333
-  assertEquals(42, %_CallFunction(null, 11, 31, f))
-  assertSame(isStrict ? null : global_object, receiver)
 
   var ff = Function.prototype.bind.call(f, o, 12)
   assertTrue(ff.length <= 1)  // TODO(rossberg): Not spec'ed yet, be lax.
   receiver = 333
   assertEquals(42, ff(30))
   assertSame(o, receiver)
   receiver = 333
   assertEquals(33, Function.prototype.call.call(ff, {}, 21))
   assertSame(o, receiver)
   receiver = 333
@@ skipping 629 matching lines @@
   with (this) {
     assertEquals(this, fp());
     assertEquals(this, gp());
   }
 
   with ({}) {
     assertEquals(Realm.shared.fg, fp());
     assertEquals(Realm.shared.gg, gp());
   }
 }