fix. Stylus button press changes tool to Eraser but do not erase.

[QubaB]

Some styluses do not send move events when button is pressed. So Eraser do not work.

This change allows switch to eraser by pressing and releasing stylus button (no more holding button), then erasing items work.

Creates new preference, which can change default behavior of pressing button when pen is above screen.

Solves issue #1410

[codecov]

Codecov Report

❌ Patch coverage is 37.50000% with 15 lines in your changes missing coverage. Please review.
✅ Project coverage is 47.15%. Comparing base (7d60459) to head (04e94e0).
⚠️ Report is 511 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/pages/editor/editor.dart	16.66%	15 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1428      +/-   ##
==========================================
- Coverage   47.15%   47.15%   -0.01%     
==========================================
  Files         114      114              
  Lines        9002     9018      +16     
==========================================
+ Hits         4245     4252       +7     
- Misses       4757     4766       +9     

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[adil192]

@QubaB Thanks for the fix.

Please add some tests for this behaviour with and without the eraserOnStylusButtonPressAndRelease setting.

Also, the setting is a bit confusing at the moment: I think the most understandable UI would be to have two selection options (in an enum) for "Press stylus button to toggle eraser" and "Hold stylus button down for eraser".