fix(echarts): Series labels hard to read in dark mode (#34815)

superset-frontend/plugins/plugin-chart-echarts/src/MixedTimeseries/transformProps.ts

@@ -450,6 +450,7 @@ export default function transformProps(
         showValueIndexes: showValueIndexesA,
         thresholdValues,
         timeShiftColor,
+        theme,
       },
     );
     if (transformedSeries) series.push(transformedSeries);
@@ -516,6 +517,7 @@ export default function transformProps(
         showValueIndexes: showValueIndexesB,
         thresholdValues: thresholdValuesB,
         timeShiftColor,
+        theme,
       },
     );
     if (transformedSeries) series.push(transformedSeries);

superset-frontend/plugins/plugin-chart-echarts/src/Timeseries/transformProps.ts

@@ -331,6 +331,7 @@ export default function transformProps(
         lineStyle,
         timeCompare: array,
         timeShiftColor,
+        theme,
       },
     );
     if (transformedSeries) {

superset-frontend/plugins/plugin-chart-echarts/src/Timeseries/transformers.ts

@@ -168,6 +168,7 @@ export function transformSeries(
     queryIndex?: number;
     timeCompare?: string[];
     timeShiftColor?: boolean;
+    theme?: SupersetTheme;
   },
 ): SeriesOption | undefined {
   const { name, data } = series;
@@ -197,6 +198,7 @@ export function transformSeries(
     queryIndex = 0,
     timeCompare = [],
     timeShiftColor,
+    theme,
   } = opts;
   const contexts = seriesContexts[name || ''] || [];
   const hasForecast =
@@ -323,6 +325,8 @@ export function transformSeries(
     label: {
       show: !!showValue,
       position: isHorizontal ? 'right' : 'top',
+      color: theme?.colorText,
+      textBorderWidth: 0,
       formatter: (params: any) => {
         // don't show confidence band value labels, as they're already visible on the tooltip
         if (