Integrate Blockly keyboard controls

[tracygardner]

Already 'enabled' (technically included). Doesn't seem to break mouse behaviours so leaving on.

Various issues including:

• List blocks mutator buttons get focus and work but there is no visual focus highlight
• You have to press Tab to get to grid inputs, is that intuitive?
• Focus highlight not clear on grid editors (such as color) @lawsie
• Mutator buttons on custom blocks don't have focus highlight (but do work)
• Comment style does change on focus but subtle and not consistent @lawsie
• We get a additional blue focus highlight around the workspace and toolbox. Not needed. @lawsie
• Related to above. We don't get a workspace focus highlight when the workspace hitself has focus, e.g. via W @lawsie
• Esc should close block comments - fixed in v13 beta
• Enter should edit text input blocks without having to navigate right. They technically have a nested input but the user shouldn't have to worry about that.
• Context menu not appearing with v13 beta
• Ctrl + Enter context menu on the workspace sometimes appears off screen
• Esc doesn't close block context menu or dropdowns
• Esc doesn't close workspace context menu
• Style toast messages to match Flock @lawsie - removed in Blockly 13?
• Add translation for toast messages @lawsie - removed in Blockly 13?
• When changing the model in a dropdown the input gets passive focus afterwards
• Integrate Tab handling for workspace comments
• Don't show keyboard controls paste toast when copy is triggered from the context menu (but show when triggered using keyboard controls)
• Esc should close the toolbox flyout. If keyboard focus was on the toolbox then it should return there.
• Can the trashcan be made to work with keyboard controls?
• Add passive keyboard focus to blockly blocks when selected via gizmo Select tool highlights blockly block but KB focus doesn't move #564
• Need to reimplement layoutTopLevel blocks to work with new focus handling for keyboard nav

[lawsie]

Relevant PRs

• Integrate blockly kb controls #625

[tracygardner]

Added visual focus highlight for mutator buttons. 2de8446

Includes passive highlight:

[tracygardner]

Gizmo handling was stopping propagation of Esc and preventing close of dropdowns and context menus 0e8dec2

[tracygardner]

Esc takes two presses to close a block comment. This matches Blockly behaviour but doesn't seem intuitive.

[tracygardner]

Copy from the context menu was generating a keyboard controls toast even when keyboard controls are not used (including on mobile).

e2d50b7 limits this to when keyboard copy shortcut is used.

[tracygardner]

Updated to the blockly v13 beta 3 to get closer to final keyboard navigation behaviour 1301d8a