Fix @elastic/eui/require-table-caption lint violations in drilldown manager UI (#271377)

Two `EuiInMemoryTable` instances in the drilldown manager UI were
missing the required `tableCaption` prop, violating
`@elastic/eui/require-table-caption`.

### Changes

- **`drilldown_template_table`** — Added `tableCaption` with i18n
string: *"Drilldown templates"*
- **`drilldown_table`** — Added `tableCaption` with i18n string:
*"Drilldowns"*

```tsx
<EuiInMemoryTable
  tableCaption={txtTableCaption}
  items={drilldowns}
  // ...
/>
```

Captions describe the dataset per EUI accessibility guidelines and use
`i18n.translate` for localization.

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: Alexey Antonov <alexwizp@gmail.com>

Author: Copilot

src/platform/plugins/shared/embeddable/public/drilldowns/drilldown_manager_ui/components/drilldown_table/drilldown_table.tsx

@@ -18,6 +18,7 @@ import {
   txtEditDrilldown,
   txtCloneDrilldown,
   txtSelectDrilldown,
+  txtTableCaption,
   txtName,
   txtAction,
   txtTrigger,
@@ -144,6 +145,7 @@ export const DrilldownTable: React.FC<DrilldownTableProps> = ({
         itemId="id"
         columns={columns}
         responsiveBreakpoint={false}
+        tableCaption={txtTableCaption}
         selection={{
           onSelectionChange: (selection) => {
             setSelectedDrilldowns(selection.map((drilldown) => drilldown.id));

src/platform/plugins/shared/embeddable/public/drilldowns/drilldown_manager_ui/components/drilldown_table/i18n.ts

@@ -38,6 +38,13 @@ export const txtDeleteDrilldowns = (count: number) =>
     },
   });
 
+export const txtTableCaption = i18n.translate(
+  'embeddableApi.components.DrilldownTable.tableCaption',
+  {
+    defaultMessage: 'Drilldowns',
+  }
+);
+
 export const txtSelectDrilldown = i18n.translate(
   'embeddableApi.components.DrilldownTable.selectThisDrilldownCheckboxLabel',
   {

src/platform/plugins/shared/embeddable/public/drilldowns/drilldown_manager_ui/components/drilldown_template_table/drilldown_template_table.tsx

@@ -17,6 +17,7 @@ import {
   txtSingleItemCopyActionLabel,
   txtActionColumnTitle,
   txtTriggerColumnTitle,
+  txtTableCaption,
 } from './i18n';
 import { TextWithIcon } from '../text_with_icon';
 import { TriggerLineItem } from '../trigger_line_item';
@@ -117,6 +118,7 @@ export const DrilldownTemplateTable: React.FC<DrilldownTemplateTableProps> = ({
           },
           selectableMessage: () => txtSelectableMessage,
         }}
+        tableCaption={txtTableCaption}
       />
       <EuiSpacer />
       {!!onClone && !!selected.length && (

src/platform/plugins/shared/embeddable/public/drilldowns/drilldown_manager_ui/components/drilldown_template_table/i18n.ts

@@ -54,6 +54,13 @@ export const txtSingleItemCopyActionLabel = i18n.translate(
   }
 );
 
+export const txtTableCaption = i18n.translate(
+  'embeddableApi.components.DrilldownTemplateTable.tableCaption',
+  {
+    defaultMessage: 'Drilldown templates',
+  }
+);
+
 export const txtCopyButtonLabel = (count: number) =>
   i18n.translate('embeddableApi.components.DrilldownTemplateTable.copyButtonLabel', {
     defaultMessage: 'Copy ({count})',