[Vis Colors] Replace color maps with explicit OUI color palettes

[BSFishy]

#4293 (comment)

The color palettes used in color maps could be refactored to generate the palette on demand, rather than having a static palette and choosing specific colors off of it. Most likely, the best way to do this would be to make the color maps contain a function with 1 argument, the size of the palette, and return the palette of correct size. I.e. something like

  [ColorSchemas.Blues]: {
    id: ColorSchemas.Blues,
    label: i18n.translate('charts.colormaps.bluesText', {
      defaultMessage: 'Blues',
    }),
    generate: (length) => ouiPaletteCool(length),
  },
  [ColorSchemas.YellowToRed]: {
    id: ColorSchemas.YellowToRed,
    label: i18n.translate('charts.colormaps.yellowToRedText', {
      defaultMessage: 'Yellow to Red',
    }),
    generate: (length) =>
      ouiColorPalette(
        [euiThemeVars.euiColorWarning, euiThemeVars.euiColorDanger],
        length,
        false,
        true
      ),
  },

  // etc...