[bgw-gui] Added lock() and unlock() to MenuScene

[smilefx]

Additionally fixed lockedProperty not being respected if locking was used in init block.

[codecov]

Codecov Report

Attention: Patch coverage is 6.25000% with 15 lines in your changes are missing coverage. Please review.

Project coverage is 14.94%. Comparing base (266db43) to head (98217f1).

Files	Patch %	Lines
...main/kotlin/tools/aqua/bgw/builder/SceneBuilder.kt	0.00%	13 Missing ⚠️
...w-gui/src/main/kotlin/tools/aqua/bgw/core/Scene.kt	33.33%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #409      +/-   ##
==========================================
- Coverage   14.95%   14.94%   -0.02%     
==========================================
  Files         288      288              
  Lines        7744     7756      +12     
  Branches     1058     1062       +4     
==========================================
+ Hits         1158     1159       +1     
- Misses       6501     6512      +11     
  Partials       85       85              

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