kaizen: clean up state finite automata

[timbray]

addresses #197

This gets rid of the DFA/NFA distinction, everything is now an NFA. The stretch goal is to fix #188, but the messy sprawl of DFA-and-NFA was getting in the way of understanding.

This includes a bunch of commented-out code for pretty-printing state machines, which I found totally essential in migrating to all-NFA. I'm going to create an issue to bring this code out of comments and make it possible to switch it off/on to facilitate the creating and merging different kinds of patterns.

[timbray]

I see that I accidentally lost a couple of unit tests, although the coverage didn't go down. Will clean this up subsequently. There's a huge amount of quite difficult work here that I want to get checked in so I have a stable base to continue work on #188 and then some new features.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 97.80220% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 96.32%. Comparing base (a716bc1) to head (8351137).
Report is 68 commits behind head on main.

Files	Patch %	Lines
nfa.go	94.82%	1 Missing and 2 partials ⚠️
shell_style.go	95.45%	1 Missing ⚠️

❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #308      +/-   ##
==========================================
+ Coverage   96.19%   96.32%   +0.13%     
==========================================
  Files          17       17              
  Lines        2129     1634     -495     
==========================================
- Hits         2048     1574     -474     
+ Misses         54       34      -20     
+ Partials       27       26       -1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[timbray]

Having thought about it, I can see why this is a difficult PR to review. It's all down in the finite-automaton weeds and not that many people care about this stuff or have exposure to it. Having said that, a bunch of ugly code was removed and the tests all still pass and I see no performance regression. So I will probably break the rules and go ahead and merge if nobody is up to doing a real review in the next day or so.

[embano1]

+1