[ui][fix] Edge: Fixing an issue with mouse event on Custom EdgeMouseArea causing Crash

[waaake]

Event::button() was sometimes causing a crash, copying the event and using event.buttons() from the copied event seems to be stable before calling event.button() eventually

Description

This PR addresses a known crash issue with the EdgeMouseArea (QQuickItem)'s mousePressEvent.
The crash occurs when querying button() from the event.
The event is not null and is able to provide other data correctly before ending up crashing when queried for button.

Features list

• Fix UpdateShape to get invoked on geometryChange
• Fix Alt + Mouse Click to Remove an Edge due to a change in data type for Keyboard Modifiers from int to enum.Flag
• Fix Crash on clicking egde multiple times

Implementation remarks

Current Fix is based on copying the provided event and calling event.buttons() to check if the buttons are supported and then calling button() is the custom MouseEvent constructor.
This seems to have stopped the crashes for now, but still testing on larger scale is pending before we confirm anything.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 69.96%. Comparing base (6071a91) to head (870dcf4).
Report is 17 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2650      +/-   ##
===========================================
+ Coverage    69.93%   69.96%   +0.02%     
===========================================
  Files          121      121              
  Lines         7088     7084       -4     
===========================================
- Hits          4957     4956       -1     
+ Misses        2131     2128       -3     

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