Implement copy/deepcopy for Triangulation/VoronoiTessellation

[DanielVandH]

Fixes #142

[codecov]

Codecov Report

Attention: Patch coverage is 99.50249% with 1 line in your changes missing coverage. Please review.

Project coverage is 94.84%. Comparing base (8606710) to head (1bb8bfe).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...ta_structures/mesh_refinement/boundary_enricher.jl	97.56%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #201      +/-   ##
==========================================
- Coverage   94.97%   94.84%   -0.13%     
==========================================
  Files         103      103              
  Lines       10215    10367     +152     
==========================================
+ Hits         9702     9833     +131     
- Misses        513      534      +21     

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