WFA: make match() function 'const'
Fix comment
WFA genericWpdsPoststar: don't put in a delta-2 rule if unneeded
WFA::complete: Improve sink state handling

- Make a copy of the states to avoid modification concurrent to traversal
- Don't try to add duplicate transitions
WFA::intersect refactoring: extract method for most of worklist handling
WFA::intersect: refactoring extract method to add a state if necessary
WFA::intersect_worklist: rework epsilon transition handling

Now instead of taking the epsilon closure, the intersected automaton will have epsilon transitions to possible configurations.
WFA::intersect: properly track accepting weights
WFA::intersect: don't do epsilon closure at the beginning now either

The previous changes subsume the nonsense I used to do.