[10.x] Add clear() method to facade fakes

[jerodev]

When testing using facade fakes, it used to be possible to override the facade by faking again to reset the state. Since #46188, this is no longer possible.

This PR includes a clear() function on these facades that allows clearing the internal queue/event/... history.

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For example, I used to do the following to test notifications over a span of time:

$this->sendReminders();
Notification::assertSentTo($user, ReminderMail::class);

Notification::fake();
$this->travel(3)->days();
$this->sendReminders();
Notification::assertNothingSent();

Notification::fake();
$this->travel(6)->days();
$this->sendReminders();
Notification::assertSentTo($user, ReminderMail::class);

This new clear method can now be used instead to clear the internal $notifications array.

[driesvints]

Thanks but we're going to be reverting all of these PRs up till the original one that started the chain of breaking changes.

[driesvints]

@jerodev we decided to fix it differently: #46257

Can you confirm if that works for you?

[jerodev]

Can you confirm if that works for you?

@driesvints All tests successful here, thanks! 👍