Use undefined as this in trusted type callbacks (#37594)

As discussed in w3c/trusted-types#468 the spec will be aligned to the
other browsers, which call the callback with undefined as this.

That also allows us to cleanup the JSContext arguments across a couple
of methods.

Signed-off-by: Tim van der Lippe <tvanderlippe@gmail.com>

tests/wpt/meta/MANIFEST.json

@@ -824957,7 +824957,7 @@
      ]
     ],
     "TrustedTypePolicy-createXXX.html": [
-     "f51f51d98455ebccdee31a5b0d844a926b27fc0e",
+     "957a691bcd909d71b2b34a4256fe7168cd14930b",
      [
       null,
       {}