LibJS: Use TimeZoneMethods in GetOffsetNanosecondsFor

Update to the latest version of the spec which was refactored to use
time zone methods record. This requires updating a whole bunch of
callers to pass through a record too.

This also ends up improving exceptions on a missing
getOffsetNanosecondsFor method.

Userland/Libraries/LibJS/Tests/builtins/Temporal/TimeZone/TimeZone.prototype.getPlainDateTimeFor.js

@@ -35,7 +35,7 @@ describe("errors", () => {
         const instant = new Temporal.Instant(1n);
         expect(() => {
             timeZone.getPlainDateTimeFor(instant);
-        }).toThrowWithMessage(TypeError, "null is not a function");
+        }).toThrowWithMessage(TypeError, "getOffsetNanosecondsFor is undefined");
     });
 
     test("this value must be a Temporal.TimeZone object", () => {