Fix shape group mouse-transparency when drawing

[mfl28]

• Sets bounding shape group mouse-transparent whenever shape drawing is initialized and resets it on drawing-finalization. This presents bounding shapes from intercepting mouse events while drawing is in progress.
• Adds mouse-transparency checks to bounding shape drawing tests.

Fixes #111.

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
1 Code Smell

100.0% Coverage
0.0% Duplication

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (41df50f) 86.46% compared to head (b076cca) 86.46%.

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #112   +/-   ##
=========================================
  Coverage     86.46%   86.46%           
+ Complexity     1482     1480    -2     
=========================================
  Files            95       95           
  Lines          5933     5933           
  Branches        534      534           
=========================================
  Hits           5130     5130           
  Misses          527      527           
  Partials        276      276           

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