Fix copy and deepcopy for PolygonTrees and PolygonHierarchys

[DanielVandH]

Fixes #129

[codecov]

Codecov Report

Attention: Patch coverage is 88.09524% with 5 lines in your changes missing coverage. Please review.

Project coverage is 94.97%. Comparing base (296255b) to head (8d2b872).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/data_structures/trees/polygon_hierarchy.jl	88.09%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #199      +/-   ##
==========================================
- Coverage   95.00%   94.97%   -0.04%     
==========================================
  Files         102      102              
  Lines       10187    10200      +13     
==========================================
+ Hits         9678     9687       +9     
- Misses        509      513       +4     

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