Use vm flags for zend_optimizer_migrate_jump()

[iluuu1994]

@dstogov I'm planning on using making a bunch of such suggestions, if you think they are ok. The goal is to minimize changes in optimizer when adding new opcodes, because:

1. It's tedious.
2. Most contributors shouldn't need to understand the optmizer, and minimizing the necessary changes will simplify things for them.

[dstogov]

I think the proposed code is going to be slower.
Instead, it may make sense to add assertions into default path.
This way we will be sure that nothing is missed.