Add current scene to the Unity context

[lucas-zimerman]

Having the Scene as a tag helps you to filter the errors that may be happening on a given scene (although this may not help if there's a native crash?)

[bitsandfoxes]

That's a great idea! We could set the scene as Transaction. The LogHandler now possibly has the GameObject as context and we could get the scene it belongs to from there.

[vaind]

Later we can do the tag from the Unity context item, if needed (during ingestion).

[vaind]

We need to find out how often the GameObject is actually available.

P.S. we may want to also add the GameObject class to the context.

[bitsandfoxes]

Added in #2084