Continue test harness execution if zone doesn't stabilize within a certain amount of time

Currently the test harnesses wait for the zone to stabilize before executing, however there are some cases where it might not happen. For example, in https://github.com/angular/components/issues/23964 the test times out because a Material component uses `requestAnimationFrame` which the browser can decide to pause if it's out of view.

One thing to consider is that Jasmine tests time out after 5s by default so we should pick a number that is lower.

Start by locating the test harness code that waits for zone stabilization, then inspect how Jasmine's default 5-second timeout applies to these tests. Reproduce the requestAnimationFrame scenario described in angular/components#23964. Done means the harness continues when stabilization does not occur within a shorter limit, while normal stabilized execution remains unchanged.

Written by the indexing model from the issue text.