MAINT: Refactor `test_plotting.py`

[nawtrey]

• Refactor all 3 testing functions, test_draw_cycles, test_draw_diagrams, and test_draw_ode_results, to use parametrization

• Change all 3 test functions to save the figure in a temporary directory to increase code coverage and close the figures

• Move flux diagram code for 4 state model with leakage to its own function-scoped pytest fixture

• Simplify fixtures G4wl, pos_4wl, and results_4wl

• Remove unused imports

• Rename draw_ODE_results to draw_ode_results

[codecov[bot]]

Codecov Report

Merging #43 (2022d56) into master (c4843b1) will increase coverage by 1.87%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #43      +/-   ##
==========================================
+ Coverage   97.99%   99.86%   +1.87%     
==========================================
  Files           9        9              
  Lines         747      747              
==========================================
+ Hits          732      746      +14     
+ Misses         15        1      -14     

Impacted Files	Coverage Δ
kda/plotting.py	100.00% <100.00%> (+6.93%)	:arrow_up:

[nawtrey]

Tests pass, coverage for this module is increased to 100%. Merging.