Use Lock.Scope throughout the project

[Haselnussbomber]

While a lock block on a Lock object is translated into an EnterScope call on compile, doing it explicitly feels cleaner and also uncovered that a couple locks were still on objects/Lists instead. Using lock on an object makes it use the legacy Monitor class, which has some overhead.

I suggest to review without whitespace changes. :)
Hope I didn't break anything. 😇

[Haselnussbomber]

Rebased to fix merge conflicts. :)