Remove usage of srand() and rand() functions

[corentin-prigent]

2D mesh generation is comprised of two steps:

1. Insertion of all points given by the user, using Delaunay method, regardless of any user-provided edges.
2. Verification that all user-provided edges are in the mesh. If some edges are missing, enforce their presence by performing swaps.

The second step uses srand() and rand() functions in order to travel missing edges (that are being enforced) in a random order. This could lead some outputs to be non-deterministic if some edges were not possible to enforce.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 50.25%. Comparing base (4e2f535) to head (9464990).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #304      +/-   ##
===========================================
- Coverage    50.31%   50.25%   -0.07%     
===========================================
  Files          177      177              
  Lines        47881    47895      +14     
  Branches     10362    10361       -1     
===========================================
- Hits         24093    24070      -23     
- Misses       16047    16087      +40     
+ Partials      7741     7738       -3     

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