Add block-centroids to tax-lot layergroup

[chriswhong]

We have this hard coded in two places in applicantmaps. The pluto source already contains the data, but there is no layergroup in this service that uses it. We should either add it to tax-lots or make a separate layergroup.

{
          style: {
            id: 'block-labels',
            type: 'symbol',
            source: 'pluto',
            'source-layer': 'block-centroids',
            minzoom: 14,
            maxzoom: 24,
            layout: {
              'text-field': '{block}',
              'text-font': [
                'Open Sans Bold',
                'Arial Unicode MS Regular',
              ],
              'text-size': 22,
            },
            paint: {
              'text-halo-color': 'rgba(255, 255, 255, 0.5)',
              'text-halo-width': 1,
              'text-color': 'rgba(121, 121, 121, 1)',
              'text-halo-blur': 0,
              'text-opacity': {
                stops: [
                  [
                    14,
                    0,
                  ],
                  [
                    15,
                    1,
                  ],
                ],
              },
            },
          },
        },