These tests were mostly async tests written in a manual way. This ports
them to use the standard asyncTest() infrastructure.
This is mostly just to reduce calls to internals.signalTextTestIsDone,
which will have a required parameter in an upcoming test.
While waiting for a task that populates a session history entry, we
can't limit the processing of the event loop to the
`NavigationAndTraversal` task source. This is because fetching uses the
`Networking` task source, which also needs to be processed.
Since making a fetch request might take some time, we want to process
everything on the event loop while waiting, to avoid blocking user
interactions.
It is still possible to use `spin_processing_tasks_with_source_until()`
on subsequent steps of `apply_the_history_step()`.
Also modifies test that was flaky.
In our implementation of the "apply the history step" algorithm, we
have to spin-wait for the completion of tasks queued on the event loop.
Before this change, we allowed tasks from any source to be executed
while we were waiting. It should not be possible because it allows to
interrupt history step application by anything, including another
history step application.
Fixes https://github.com/SerenityOS/serenity/issues/23598
