Deprecate Search Session UX (#187923)

## Summary

Part of #186334.

Adds a deprecation message to the main components of the Search Sessions
feature: the pop-up indicator (used to save search sessions) and the
management page (used to restore search sessions).

Search sessions indicator:


![image](https://github.com/elastic/kibana/assets/1178348/78c9f078-f01c-4a80-bc30-b60016586a76)

Search sessions management UX:


![image](https://github.com/elastic/kibana/assets/1178348/8bbe483a-94e7-41d6-98ca-3e82872a6057)

### Checklist

- [x] Any text added follows [EUI's writing
guidelines](https://elastic.github.io/eui/#/guidelines/writing), uses
sentence case text and includes [i18n
support](https://github.com/elastic/kibana/blob/main/packages/kbn-i18n/README.md)
- [ ]
[Documentation](https://www.elastic.co/guide/en/kibana/master/development-documentation.html)
was added for features that require explanation or tutorials
- [ ] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios

### Release note

Search Sessions are deprecated and will be removed in a future version.

src/plugins/data/public/search/session/search_sessions_deprecation_message.tsx

@@ -0,0 +1,40 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+import React from 'react';
+import { i18n } from '@kbn/i18n';
+import { FormattedMessage } from '@kbn/i18n-react';
+import { EuiCallOut } from '@elastic/eui';
+
+const searchSessionsDeprecatedWarningTitle = i18n.translate(
+  'data.searchSessionIndicator.deprecationWarning.title',
+  {
+    defaultMessage: 'Deprecated in 8.15.0',
+  }
+);
+
+export interface SearchSessionsDeprecatedWarningProps {
+  size?: 's' | 'm';
+}
+
+export const SearchSessionsDeprecatedWarning = ({
+  size = 'm',
+}: SearchSessionsDeprecatedWarningProps) => (
+  <EuiCallOut
+    title={searchSessionsDeprecatedWarningTitle}
+    size={size}
+    color="warning"
+    iconType="help"
+    data-test-subj="searchSessionsDeprecatedWarningTitle"
+  >
+    <FormattedMessage
+      id="data.searchSessionIndicator.deprecationWarning.textParagraphOne"
+      defaultMessage="Search Sessions are deprecated and will be removed in a future version."
+    />
+  </EuiCallOut>
+);

src/plugins/data/public/search/session/session_indicator/search_session_indicator/search_session_indicator.tsx

@@ -27,6 +27,7 @@ import { CheckInEmptyCircle, PartialClock } from './custom_icons';
 import './search_session_indicator.scss';
 import { SearchSessionName } from './components';
 import { SearchSessionState } from '../../search_session_state';
+import { SearchSessionsDeprecatedWarning } from '../../search_sessions_deprecation_message';
 
 export interface SearchSessionIndicatorProps {
   state: SearchSessionState;
@@ -404,6 +405,9 @@ export const SearchSessionIndicator = React.forwardRef<
       }
     >
       <div data-test-subj="searchSessionIndicatorPopoverContainer">
+        <SearchSessionsDeprecatedWarning size="s" />
+        <EuiSpacer size="m" />
+
         {props.searchSessionName && props.saveSearchSessionNameFn ? (
           <SearchSessionName
             name={props.searchSessionName}

src/plugins/data/public/search/session/sessions_mgmt/components/main.tsx

@@ -13,6 +13,7 @@ import type { CoreStart, HttpStart } from '@kbn/core/public';
 import type { SearchSessionsMgmtAPI } from '../lib/api';
 import type { AsyncSearchIntroDocumentation } from '../lib/documentation';
 import { SearchSessionsMgmtTable } from './table';
+import { SearchSessionsDeprecatedWarning } from '../../search_sessions_deprecation_message';
 import { SearchSessionsConfigSchema } from '../../../../../config';
 import { SearchUsageCollector } from '../../../collectors';
 
@@ -58,6 +59,9 @@ export function SearchSessionsMgmtMain({ documentation, ...tableProps }: Props)
         ]}
       />
 
+      <EuiSpacer size="l" />
+      <SearchSessionsDeprecatedWarning />
+
       <EuiSpacer size="l" />
       <SearchSessionsMgmtTable data-test-subj="search-sessions-mgmt-table" {...tableProps} />
     </>