detect: improve stateful detection

detect: improve stateful detection

Now that MPM runs when the TX progress is right, stateful detection
operates differently.

Changes:

1. raw stream inspection is now also an inspect engine

   Since this engine doesn't take the transactions into account, it
   could potentially run multiple times on the same data. To avoid
   this, basic result caching is in place.

2. the engines are sorted by progress, but the 'MPM' engine is first
   even if the progress is higher

   If MPM flags a rule to be inspected, the inspect engine for that
   buffer runs first. If this step fails, the rule is no longer
   evaluated. No state is stored.