[Discover] Replace deprecated page components (#162836)

- Closes https://github.com/elastic/kibana/issues/161426

## Summary

This PR updates usage of Eui page components for the following plugins.
Also took this opportunity to make these pages a little nicer.

### src/plugins/data_view_management

Before:
<img width="600" alt="Screenshot 2023-07-31 at 20 09 28"
src="5b52d31d-b759-40f9-8a8e-d428f6431f45">

After:
<img width="600" alt="Screenshot 2023-07-31 at 20 09 37"
src="dfd738d9-fa19-41d2-a55e-6157d9f2310a">


### examples/search_examples

Before:
<img width="600" alt="Screenshot 2023-07-31 at 17 41 03"
src="cc739f2d-bbaa-4cae-80d8-27599170a40a">

After:
<img width="600" alt="Screenshot 2023-07-31 at 18 01 47"
src="ab596aae-f9b4-48f0-8401-a507f4814624">

Before:
<img width="600" alt="Screenshot 2023-07-31 at 20 30 19"
src="40327fdd-7161-4d65-86ff-ff38455477fb">

After:
<img width="600" alt="Screenshot 2023-07-31 at 20 30 39"
src="8455c09f-6d84-4ad1-9e25-f8555a4f40db">

Before:
<img width="600" alt="Screenshot 2023-07-31 at 18 20 47"
src="68b05f4a-fcc0-4051-92b4-88a34bd22fb6">

After:
<img width="600" alt="Screenshot 2023-07-31 at 18 44 32"
src="1fd00e7e-3663-470f-927a-b7d7a0fe6c20">

### examples/partial_results_example

Before:
<img width="600" alt="Screenshot 2023-07-31 at 17 29 32"
src="589a2d93-c42a-4948-b805-0447e96f8ae4">

After:
<img width="600" alt="Screenshot 2023-07-31 at 17 31 52"
src="22df2b40-a9ec-4e11-b4dc-19da86c73059">

### examples/field_formats_example

Before:
<img width="600" alt="Screenshot 2023-07-31 at 17 27 44"
src="d3fa1fc3-e3e2-4f69-87e5-7187f8d3b000">

After:
<img width="600" alt="Screenshot 2023-07-31 at 17 27 56"
src="5633dba4-85ed-4767-bc8c-dee0c4da8798">

### examples/data_view_field_editor_example

Before:
<img width="600" alt="Screenshot 2023-07-31 at 17 33 15"
src="0be36a57-aef3-4679-ac77-9d5073b72fc2">

After:
<img width="600" alt="Screenshot 2023-07-31 at 17 37 34"
src="e43b0a1d-12fe-4d06-90b0-63cbc36e5ac2">


### Checklist

- [x] This renders correctly on smaller devices using a responsive
layout. (You can test this [in your
browser](https://www.browserstack.com/guide/responsive-testing-on-local-server))
- [x] This was checked for [cross-browser
compatibility](https://www.elastic.co/support/matrix#matrix_browsers)

examples/data_view_field_editor_example/public/app.tsx

@@ -13,11 +13,8 @@ import {
   EuiFlexGroup,
   EuiFlexItem,
   EuiInMemoryTable,
-  EuiPage,
-  EuiPageBody,
-  EuiPageContent_Deprecated as EuiPageContent,
-  EuiPageContentBody_Deprecated as EuiPageContentBody,
-  EuiPageHeader,
+  EuiPageTemplate,
+  EuiSpacer,
   EuiText,
   useGeneratedHtmlId,
 } from '@elastic/eui';
@@ -86,6 +83,7 @@ const DataViewFieldEditorExample = ({ dataView, dataViewFieldEditor }: Props) =>
   const content = dataView ? (
     <>
       <EuiText data-test-subj="dataViewTitle">Data view: {dataView.title}</EuiText>
+      <EuiSpacer />
       <EuiFlexGroup alignItems="center">
         <EuiFlexItem grow={false}>
           <EuiButton
@@ -118,6 +116,7 @@ const DataViewFieldEditorExample = ({ dataView, dataViewFieldEditor }: Props) =>
           />
         </EuiFlexItem>
       </EuiFlexGroup>
+      <EuiSpacer size="s" />
       <EuiInMemoryTable<DataViewField>
         items={fields}
         columns={columns}
@@ -136,14 +135,10 @@ const DataViewFieldEditorExample = ({ dataView, dataViewFieldEditor }: Props) =>
   );
 
   return (
-    <EuiPage>
-      <EuiPageBody>
-        <EuiPageHeader>Data view field editor demo</EuiPageHeader>
-        <EuiPageContent>
-          <EuiPageContentBody>{content}</EuiPageContentBody>
-        </EuiPageContent>
-      </EuiPageBody>
-    </EuiPage>
+    <EuiPageTemplate offset={0}>
+      <EuiPageTemplate.Header pageTitle="Data view field editor demo" />
+      <EuiPageTemplate.Section>{content}</EuiPageTemplate.Section>
+    </EuiPageTemplate>
   );
 };