Make block holder and toolbar look nicer

[koke]

Note: This needs WordPress/gutenberg#12403 to be merged first

Some changes to make the block holder look better:

• Uses dashicons instead of Emoji
• Update layout so buttons have the expected size (44x44)
• Remove unused settings button
• Push the delete button to the right
• Disable up/down when you can't move a block (it's the first or last)
• Added borders to the block holder when focused
• A bit of a refactor and better folder structure for InlineToolbar

@iamthomasbishop I know your mockups use Gridicons, but we still don't have those available, and dashicons are already quite an improvement over emoji 😉. Also, I used $light-gray-500 for the block borders, but I'm not sure if it's the right one, I think your mockups looked more blue than this

[marecar3]

Adding @iamthomasbishop.

[koke]

After talking to Thomas, I still have to:

• Add the palette we're using in the apps to the project
• Switch the color of the inactive arrows and borders to grey-lighten-30
• Switch the color of the active buttons to #7b9ab1

[koke]

This needs WordPress/gutenberg#12403 to be merged first

[koke]

Ready for another look:

[marecar3]

Approved :)

[marecar3]

Hey @koke, did you maybe consider using ToolbarButton e.g.<ToolbarButton label={ __( 'Undo' ) } icon="undo" isDisabled={ ! hasUndo } onClick={ undo } /> ?
As it's the same as what you have created here?