Cleanup actor creation

[Stebalien]

Currently, there are two code-paths for actor creation:

1. Implicitly created actor accounts.
2. Explicitly created actors (from the init actor).

Both methods take entirely separate code paths.

Proposal: Use the init actor even when creating all actors, including account actors.

[Stebalien]

Note: the only reason we didn't do this before was performance. That may still apply, but it would be nice to investigate that.