Use cmake project version number in code

[benjaminwinger]

To reduce the number of places we need to update the version number, I've set up cmake to pass it as a compiler definition so it can be re-used in the C++ code.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (a616abf) 90.54% compared to head (e895007) 90.54%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2428   +/-   ##
=======================================
  Coverage   90.54%   90.54%           
=======================================
  Files        1020     1020           
  Lines       36515    36515           
=======================================
  Hits        33063    33063           
  Misses       3452     3452           

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