Initial cleanup of admin settings code + consolidate map settings

.../src/metabase/admin/settings/components/SettingHeader.jsx

.../metabase/admin/settings/components/SettingsEmailForm.jsx

...se/admin/settings/components/SettingsEmailFormElement.jsx

...rc/metabase/admin/settings/components/SettingsSetting.jsx

.../metabase/admin/settings/components/SettingsSlackForm.jsx

...etabase/admin/settings/components/SettingsUpdatesForm.jsx

...admin/settings/components/widgets/CustomGeoJSONWidget.jsx

...tabase/admin/settings/components/widgets/SettingInput.jsx

...ase/admin/settings/components/widgets/SettingPassword.jsx

...tabase/admin/settings/components/widgets/SettingRadio.jsx

...abase/admin/settings/components/widgets/SettingSelect.jsx

...abase/admin/settings/components/widgets/SettingToggle.jsx

.../metabase/admin/settings/containers/SettingsEditorApp.jsx

frontend/src/metabase/admin/settings/selectors.js

frontend/src/metabase/visualizations/PinMap.jsx

.../src/metabase/visualizations/components/ChoroplethMap.jsx

.../metabase/visualizations/components/LeafletChoropleth.jsx

...end/src/metabase/visualizations/components/LeafletMap.jsx

...etabase/visualizations/components/LeafletMarkerPinMap.jsx

.../metabase/visualizations/components/LeafletTilePinMap.jsx