fix: Fix creation of variables in the main workspace when opening flyout

[LappiLappland]

The basics

• I validated my changes

The details

Resolves

Fixes #2685

Proposed Changes

Replaced createBackingVariable manual get/set calls for variables with Blockly's helper function getOrCreateVariablePackage . It handles resolution of variable map correctly (using potentialVariableMap when in flyouts)

Reason for Changes

Blockly flyouts have VariableMap pointing to target workspace's VariableMap. Flyouts store their own VariableMap inside potentialVariableMap. Method createBackingVariable is making createVariable calls which creates variables directly on the main workspace

Test Coverage

N/A

Documentation

N/A

Additional Information

N/A

[gonfunko]

Thanks for reporting and fixing this, we really appreciate it!