More efficient chord validation

[bmcfee]

Pulling this change out of PR #377

The chord validator was compiling a monster regexp on each call, which is pretty wasteful. This PR just lifts that regexp precompilation up to the module so it can be reused. I belive this was the main inefficiency behind issue #341 .

There should be no functional changes here, so as long as it passes linting and CI I'm happy to merge.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.32%. Comparing base (7997fdf) to head (b44cb8a).
Report is 5 commits behind head on main.

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

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #378      +/-   ##
==========================================
+ Coverage   88.31%   88.32%   +0.01%     
==========================================
  Files          19       19              
  Lines        2875     2878       +3     
==========================================
+ Hits         2539     2542       +3     
  Misses        336      336              

Flag	Coverage Δ
unittests	88.32% <100.00%> (+0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

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