Use new appearanceTools flag to opt into optional UI

[kjellr]

As per WordPress/gutenberg#36646, the theme can now use 'appearanceTools': true in its theme.json file to opt into most of the design tools UI that is currently available in the theme. This can replace all of the one-off declarations below:

{
  'settings': {
    'border': {
      'color': true,
      'radius': true,
      'style': true,
      'width': true
    },
   'color': {
     'link': true
   },
    'spacing': {
      'blockGap': true,
      'margin': true,
      'padding': true
    },
    'typography': {
      'lineHeight': true
    } 
  }
}