EuiColorPalettePicker needs to allow setting data-test-subj on palettes so that functional tests can select options. Blocking elastic/kibana#69190

Should be able to pass data-test-subj to palettes and then the generated button should have data-test-subj. EuiSuperSelect allows passing data-test-subj to options list props

      {
        value: 'paletteId',
        title: 'palette titile',
        type: 'text',
        'data-test-subj': `colorMapSelectOption_${CUSTOM_COLOR_MAP}`,
      }

cc miukimiu