Equal constraints

[matscalia]

Adds the Equal and EqualRadius constraints metioned in #1979.
While I was writing the tests and adding small perturbations to test the solver I noticed that the optimizer would not converge for some Angle constraints. With the wrap around in angle_cost, the delta is always minimal and the solver converges. No tests broke and I couldn't think of any case in which this modification would actually change the already established behavior but I would ask for a double, triple check.

[matscalia]

nevermind, I definitely didn't understand how the angle constraint worked, the wrap around was a mistake. I'll fix it as soon as possible, hopefully tomorrow.

[codecov]

Codecov Report

❌ Patch coverage is 66.66667% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.96%. Comparing base (69e9514) to head (ed616e1).
⚠️ Report is 18 commits behind head on master.

Files with missing lines	Patch %	Lines
cadquery/occ_impl/sketch_solver.py	66.66%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1983      +/-   ##
==========================================
- Coverage   95.96%   94.96%   -1.01%     
==========================================
  Files          29       30       +1     
  Lines        7857     8754     +897     
  Branches     1174     1302     +128     
==========================================
+ Hits         7540     8313     +773     
- Misses        183      291     +108     
- Partials      134      150      +16     

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