Handle scipy and pytest deprecations

[martinfleis]

Follow up on #91 reported in #89.

• removing direct invocation of scipy.spatial.cKDtree which will be deprecated (use scipy.spatial.KDtree instead)
• fixing ConvexHull namespace
• fixing pytest deprecations

[codecov]

Codecov Report

Merging #109 (072cd2f) into main (44ce06b) will increase coverage by 0.18%.
The diff coverage is 94.44%.

@@            Coverage Diff             @@
##             main     #109      +/-   ##
==========================================
+ Coverage   52.38%   52.56%   +0.18%     
==========================================
  Files          12       12              
  Lines        1844     1851       +7     
  Branches      316      317       +1     
==========================================
+ Hits          966      973       +7     
  Misses        821      821              
  Partials       57       57              

Impacted Files	Coverage Δ
pointpats/geometry.py	78.57% <93.75%> (+0.93%)	⬆️
pointpats/pointpattern.py	70.05% <100.00%> (ø)