[EUI][INFRA] Updated hardcoded colors (elastic#204133)

## Summary
This PR replaces a couple of places where hardcoded colors are used in
the Infra portion of Kibana with EUITheme colors.

### Checklist

Check the PR satisfies following conditions. 

Reviewers should verify this PR satisfies this list as well.

- [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)

### Details
Below are before and after screenshots:

#### Inventory History

##### Before
<img width="721" alt="inventory history before"
src="https://github.com/user-attachments/assets/5dab5dee-aecd-4e81-8f4f-f838faeb2f66"
/>

##### After 
<img width="755" alt="Screenshot 2024-12-12 at 13 05 45"
src="https://github.com/user-attachments/assets/8d4b2d03-0326-4f69-b2b4-68550ebb6b0f"
/>


#### Alert Threshold & Alert Range annotation

##### Before 
<img width="2272" alt="Screenshot 2024-12-11 at 14 10 54"
src="https://github.com/user-attachments/assets/fa01cac2-62ff-451c-b191-5814a03840bc"
/>

##### After 
<img width="1220" alt="Screenshot 2024-12-12 at 12 58 32"
src="https://github.com/user-attachments/assets/eb4953ab-1c4d-42d1-b5ca-b5c16f0b41c5"
/>

x-pack/plugins/observability_solution/infra/public/alerting/log_threshold/components/alert_details_app_section/components/threhsold_chart/create_lens_definition.ts

@@ -78,7 +78,7 @@ function createBaseLensDefinition<D extends {}>(
             yConfig: [
               {
                 forAccessor: '607b2253-ed20-4f0a-bf62-07a1f846cca4',
-                color: '#6092c0',
+                color: euiTheme.colors.vis.euiColorVis2,
               },
             ],
           },

x-pack/plugins/observability_solution/infra/public/alerting/metric_threshold/components/alert_details_app_section.tsx

@@ -18,7 +18,6 @@ import {
   transparentize,
   useEuiTheme,
 } from '@elastic/eui';
-import chroma from 'chroma-js';
 
 import { RuleConditionChart, TopAlert } from '@kbn/observability-plugin/public';
 import { ALERT_END, ALERT_START, ALERT_EVALUATION_VALUES, ALERT_GROUP } from '@kbn/rule-data-utils';
@@ -90,7 +89,7 @@ export function AlertDetailsAppSection({ alert, rule }: AppSectionProps) {
       timestamp: alertStart!,
       endTimestamp: alertEnd ?? moment().toISOString(),
     },
-    color: chroma(transparentize('#F04E981A', 0.2)).hex().toUpperCase(),
+    color: transparentize(euiTheme.colors.danger, 0.2),
     id: `metric_threshold_${alertEnd ? 'recovered' : 'active'}_alert_range_annotation`,
   };
 

x-pack/plugins/observability_solution/infra/public/pages/metrics/inventory_view/components/timeline/timeline.tsx

@@ -10,7 +10,7 @@ import { i18n } from '@kbn/i18n';
 import { FormattedMessage } from '@kbn/i18n-react';
 import moment from 'moment';
 import { first, last } from 'lodash';
-import { EuiLoadingChart, EuiText, EuiEmptyPrompt, EuiButton } from '@elastic/eui';
+import { EuiLoadingChart, EuiText, EuiEmptyPrompt, EuiButton, useEuiTheme } from '@elastic/eui';
 import {
   Axis,
   Chart,
@@ -56,7 +56,7 @@ export const Timeline: React.FC<Props> = ({ interval, yAxisFormatter, isVisible
   const { metric, nodeType, accountId, region } = useWaffleOptionsContext();
   const { currentTime, jumpToTime, stopAutoReload } = useWaffleTimeContext();
   const { filterQueryAsJson } = useWaffleFiltersContext();
-
+  const { euiTheme } = useEuiTheme();
   const chartTheme = useTimelineChartTheme();
 
   const { loading, error, startTime, endTime, timeseries, reload } = useTimeline(
@@ -238,7 +238,11 @@ export const Timeline: React.FC<Props> = ({ interval, yAxisFormatter, isVisible
               <EuiFlexGroup gutterSize={'s'} alignItems={'center'} responsive={false}>
                 <EuiFlexItem
                   grow={false}
-                  style={{ backgroundColor: '#D36086', height: 5, width: 10 }}
+                  style={{
+                    backgroundColor: euiTheme.colors.backgroundFilledAccent,
+                    height: 5,
+                    width: 10,
+                  }}
                 />
                 <EuiFlexItem>
                   <EuiText size={'xs'}>
@@ -261,7 +265,7 @@ export const Timeline: React.FC<Props> = ({ interval, yAxisFormatter, isVisible
               dataValues={generateAnnotationData(
                 anomalies.map((a) => [a.startTime, a.influencers])
               )}
-              style={{ fill: '#D36086' }}
+              style={{ fill: euiTheme.colors.backgroundFilledAccent }}
             />
           )}
           <MetricExplorerSeriesChart