Fix static state wrong reset

[Antoshidza]

Issue

Bridge.cs uses [RuntimeInitializeOnLoadMethod] to reset it's static state. The issue is that it happens after it's own Awake() so state is being cleared right after initialization. On the next run without domain reload (which is often disable by unity devs for rapid developing) Bridge.cs still have it's _isApplicationQuitting: true which cause returning null by instance property.

In my particular case it breaks initialization of my project after first run.

What is changed

Instead of clear static state "before" something happens I think it is better to clear it in the "end" of run, so I've put logic into simple Bridge.OnDestroy().