webdriver: Wait indefinitely with None timeout

[servo-wpt-sync]

So far for None timeout, we've treated it effectively as no wait which is wrong: #57332 (comment).

This PR makes all None timeouts wait indefinitely. The funny part is, we somehow have only done it correctly for pageload: https://w3c.github.io/webdriver/#dfn-timeouts-configuration

Testing: We add test for script execution with None script timeout.
Reviewed in servo/servo#42184

[wpt-pr-bot]

The review process for this patch is being conducted in the Servo project.

[yezhizhen]

Would you like to check the test? @whimboo

Chrome is passing but Firefox is failing them. But I think there's been something wrong with Firefox's promise handling before this:
https://github.com/web-platform-tests/wpt/pull/57403/checks?check_run_id=61828175740

[yezhizhen]

This test is exactly same as

wpt/webdriver/tests/classic/execute_script/promise.py

Lines 12 to 21 in c1f157a

	def test_promise_resolve_delayed(session):
	response = execute_script(session, """
	return new Promise(
	(resolve) => setTimeout(
	() => resolve('foobar'),
	50
	)
	);
	""")
	assert_success(response, "foobar")

, except setTimeout changed from 50 to 200.

But somehow Firefox is passing test_promise_resolve_delayed but failing test_promise_resolve_timeout_none?

[whimboo]

Maybe this is related to #57160 and other recently opened issues around promises.

Can this PR wait a bit until the others have been done?

[yezhizhen]

This has nothing to do with #57160 tho. The tests here are essentially same as existing ones.