chore: Update turtle demo for v12

[rpbourret]

The basics

• I validated my changes

The details

Resolves

Fixes issue 2628.

Proposed Changes

Makes the following fixes to address the problems in the bug:

• Sets the cursor using CSS.

  • In FieldTurtle, removes the CURSOR field, removes updateEditable() (which only set the cursor), and adds a turtleField class for greater specificity.
  • In the CSS, sets the cursor type.

• Updates CSS names for v12: Changes blocklyEditableText to blocklyEditableField and blocklyNonEditableText to blocklyNonEditableField.

• In the CSS file, deletes .blocklyNonSelectable (removed in v12) and moves its rules to customFieldsTurtleWidget.

Makes the following changes, which address other problems:

• Replaces call to Block.setEnabled (removed in v12) with call to Block.setDisabledReason.

• Fixes the final set of CSS selectors, which weren't being applied because the text selector was less specific than the .blocklyText selector in .geras-renderer.classic-theme .blocklyText, which comes from renderers/common/constants.ts. As a result, the fill was set to #fff instead of #000, which the final set of selectors attempted to apply.

Reason for Changes

Test Coverage

Tested manually

Documentation

N/A

Additional Information

[BenHenning]

Thanks @rpbourret! All the changes make sense and it's nice that this is a net simplification.