[Lens] Replace scss for heatmap expression (#209246)

## Summary

Part of https://github.com/elastic/kibana/issues/208908

Replaces scss to css-in-js. 

### Checklist

- [x] The PR description includes the appropriate Release Notes section,
and the correct `release_note:*` label is applied per the
[guidelines](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process)

---------

Co-authored-by: kibanamachine <42973632+kibanamachine@users.noreply.github.com>
Co-authored-by: Marta Bondyra <4283304+mbondyra@users.noreply.github.com>

src/platform/plugins/shared/chart_expressions/expression_heatmap/public/components/heatmap_component.tsx

@@ -57,7 +57,6 @@ import {
 import { defaultPaletteParams } from '../constants';
 import { ChartSplit } from './chart_split';
 import { getSplitDimensionAccessor, createSplitPoint } from '../utils/get_split_dimension_utils';
-import './index.scss';
 
 declare global {
   interface Window {

src/platform/plugins/shared/chart_expressions/expression_heatmap/public/components/index.scss

@@ -1,10 +0,0 @@
-.heatmap-container {
-  height: 100%;
-  width: 100%;
-  // the FocusTrap is adding extra divs which are making the visualization redraw twice
-  // with a visible glitch. This make the chart library resilient to this extra reflow
-  overflow: auto hidden;
-  user-select: text;
-  padding: $euiSizeS;
-  @include euiScrollBar;
-}

src/platform/plugins/shared/chart_expressions/expression_heatmap/public/expression_renderers/heatmap_renderer.tsx

@@ -21,6 +21,8 @@ import {
   extractContainerType,
   extractVisualizationType,
 } from '@kbn/chart-expressions-common';
+import { css } from '@emotion/react';
+import { UseEuiTheme } from '@elastic/eui';
 import { MultiFilterEvent } from '../../common/types';
 import { ExpressionHeatmapPluginStart } from '../plugin';
 import {
@@ -40,6 +42,17 @@ interface ExpressioHeatmapRendererDependencies {
   getStartDeps: StartServicesGetter<ExpressionHeatmapPluginStart>;
 }
 
+const heatmapContainerCss = ({ euiTheme }: UseEuiTheme) =>
+  css({
+    width: '100%',
+    height: '100%',
+    padding: euiTheme.size.s,
+    // the FocusTrap is adding extra divs which are making the visualization redraw twice
+    // with a visible glitch. This make the chart library resilient to this extra reflow
+    overflow: 'auto hidden',
+    userSelect: 'text',
+  });
+
 export const heatmapRenderer: (
   deps: ExpressioHeatmapRendererDependencies
 ) => ExpressionRenderDefinition<HeatmapExpressionProps> = ({ getStartDeps }) => ({
@@ -101,7 +114,7 @@ export const heatmapRenderer: (
 
     render(
       <KibanaRenderContextProvider {...core}>
-        <div className="heatmap-container" data-test-subj="heatmapChart">
+        <div className="eui-scrollBar" css={heatmapContainerCss} data-test-subj="heatmapChart">
           <HeatmapComponent
             {...config}
             onClickValue={onClickValue}

src/platform/plugins/shared/chart_expressions/expression_heatmap/tsconfig.json

@@ -8,6 +8,7 @@
     "common/**/*",
     "public/**/*",
     "server/**/*",
+    "../../../../../../typings/emotion.d.ts"
   ],
   "kbn_references": [
     { "path": "../tsconfig.json" },