Add MockForward method to the scheduler that mimics going into the future by rescheduling all items on the taskQueue to be sooner.
This is a partial backport of Core [[https://github.com/bitcoin/bitcoin/pull/18037 | PR18037]] : https://github.com/bitcoin/bitcoin/pull/18037/commits/a6f63598adb880a75e1571aac58338c17fa7ad53