[Discover] [Unified Doc Viewer] Remove toasts when toggling columns (elastic#269587)

## Summary

This PR removes the success toasts shown when columns are added or
removed from the Unified Doc Viewer flyout in Discover, since it was
unnecessary. The flyout now passes the existing add/remove column
handlers through directly instead of wrapping them with success-toast
notifications.

Resolves elastic#269570.

### Checklist

- [ ] 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/src/platform/packages/shared/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
- [ ] If a plugin configuration key changed, check if it needs to be
allowlisted in the cloud and added to the [docker
list](https://github.com/elastic/kibana/blob/main/src/dev/build/tasks/os_packages/docker_generator/resources/base/bin/kibana-docker)
- [x] This was checked for breaking HTTP API changes, and any breaking
changes have been approved by the breaking-change committee. The
`release_note:breaking` label should be applied in these situations.
- [ ] [Flaky Test
Runner](https://ci-stats.kibana.dev/trigger_flaky_test_runner/1) was
used on any tests changed
- [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)
- [x] Review the [backport
guidelines](https://docs.google.com/document/d/1VyN5k91e5OVumlc0Gb9RPa3h1ewuPE705nRtioPiTvY/edit?usp=sharing)
and apply applicable `backport:*` labels.

Author: davismcphee

src/platform/plugins/shared/unified_doc_viewer/public/components/doc_viewer_flyout/doc_viewer_flyout.tsx

@@ -193,32 +193,6 @@ export function UnifiedDocViewerFlyout({
     [activePage, onClose, setPage]
   );
 
-  const addColumn = useCallback(
-    (columnName: string) => {
-      onAddColumn(columnName);
-      services.toastNotifications?.addSuccess(
-        i18n.translate('unifiedDocViewer.flyout.toastColumnAdded', {
-          defaultMessage: `Column ''{columnName}'' was added`,
-          values: { columnName },
-        })
-      );
-    },
-    [onAddColumn, services.toastNotifications]
-  );
-
-  const removeColumn = useCallback(
-    (columnName: string) => {
-      onRemoveColumn(columnName);
-      services.toastNotifications?.addSuccess(
-        i18n.translate('unifiedDocViewer.flyout.toastColumnRemoved', {
-          defaultMessage: `Column ''{columnName}'' was removed`,
-          values: { columnName },
-        })
-      );
-    },
-    [onRemoveColumn, services.toastNotifications]
-  );
-
   const docViewRenderProps = useMemo<DocViewRenderProps>(
     () => ({
       hit: actualHit,
@@ -227,8 +201,8 @@ export function UnifiedDocViewerFlyout({
       columnsMeta,
       textBasedHits: isEsqlQuery ? hits : undefined,
       filter: onFilter,
-      onAddColumn: addColumn,
-      onRemoveColumn: removeColumn,
+      onAddColumn,
+      onRemoveColumn,
       docViewsRegistry,
       decreaseAvailableHeightBy: isProjectStyle
         ? euiTheme.base + PROJECT_VIEW_MARGIN_BOTTOM
@@ -243,8 +217,8 @@ export function UnifiedDocViewerFlyout({
       isEsqlQuery,
       hits,
       onFilter,
-      addColumn,
-      removeColumn,
+      onAddColumn,
+      onRemoveColumn,
       docViewsRegistry,
       isProjectStyle,
       euiTheme.base,

x-pack/platform/plugins/private/translations/translations/de-DE.json

@@ -8868,8 +8868,6 @@
     "unifiedDocViewer.flyout.docViewerDetailHeading": "Dokument",
     "unifiedDocViewer.flyout.docViewerEsqlDetailHeading": "Ergebnis",
     "unifiedDocViewer.flyout.screenReaderDescription": "Sie befinden sich in einem nicht-modalen Dialogfenster. Um den Dialog zu schließen, drücken Sie die Escape-Taste.",
-    "unifiedDocViewer.flyout.toastColumnAdded": "Spalte „{columnName}“ wurde hinzugefügt",
-    "unifiedDocViewer.flyout.toastColumnRemoved": "Spalte „{columnName}“ wurde entfernt",
     "unifiedDocViewer.fullScreenWaterfall.logDocument.error": "Beim Abrufen des Log-Dokuments ist ein Fehler aufgetreten.",
     "unifiedDocViewer.fullScreenWaterfall.spanDocument.error": "Beim Abrufen des Span-Dokuments ist ein Fehler aufgetreten.",
     "unifiedDocViewer.hideNullValues.switchLabel": "Null-Felder ausblenden",

x-pack/platform/plugins/private/translations/translations/fr-FR.json

@@ -8869,8 +8869,6 @@
     "unifiedDocViewer.flyout.docViewerDetailHeading": "Document",
     "unifiedDocViewer.flyout.docViewerEsqlDetailHeading": "Résultat",
     "unifiedDocViewer.flyout.screenReaderDescription": "Vous êtes dans une boîte de dialogue non modale. Pour fermer la boîte de dialogue, appuyez sur Échap.",
-    "unifiedDocViewer.flyout.toastColumnAdded": "La colonne \"{columnName}\" a été ajoutée",
-    "unifiedDocViewer.flyout.toastColumnRemoved": "La colonne \"{columnName}\" a été supprimée",
     "unifiedDocViewer.fullScreenWaterfall.logDocument.error": "Une erreur s'est produite lors de la récupération du document log",
     "unifiedDocViewer.fullScreenWaterfall.spanDocument.error": "Une erreur s'est produite lors de la récupération du document Span",
     "unifiedDocViewer.hideNullValues.switchLabel": "Masquer les champs nuls",

x-pack/platform/plugins/private/translations/translations/ja-JP.json

@@ -8896,8 +8896,6 @@
     "unifiedDocViewer.flyout.docViewerDetailHeading": "ドキュメント",
     "unifiedDocViewer.flyout.docViewerEsqlDetailHeading": "結果",
     "unifiedDocViewer.flyout.screenReaderDescription": "非モーダルダイアログで操作しています。ダイアログを閉じるには、Escapeを押します。",
-    "unifiedDocViewer.flyout.toastColumnAdded": "列''{columnName}''が追加されました",
-    "unifiedDocViewer.flyout.toastColumnRemoved": "列''{columnName}''が削除されました",
     "unifiedDocViewer.fullScreenWaterfall.logDocument.error": "ログドキュメントの取得中にエラーが発生しました",
     "unifiedDocViewer.fullScreenWaterfall.spanDocument.error": "スパンドキュメントの取得中にエラーが発生しまし",
     "unifiedDocViewer.hideNullValues.switchLabel": "Nullフィールドを非表示",

x-pack/platform/plugins/private/translations/translations/zh-CN.json

@@ -8893,8 +8893,6 @@
     "unifiedDocViewer.flyout.docViewerDetailHeading": "文档",
     "unifiedDocViewer.flyout.docViewerEsqlDetailHeading": "结果",
     "unifiedDocViewer.flyout.screenReaderDescription": "您位于非模式对话框中。要关闭对话框，请按 Esc 键。",
-    "unifiedDocViewer.flyout.toastColumnAdded": "已添加列“{columnName}”",
-    "unifiedDocViewer.flyout.toastColumnRemoved": "已移除列“{columnName}”",
     "unifiedDocViewer.fullScreenWaterfall.logDocument.error": "在获取日志文档时发生错误",
     "unifiedDocViewer.fullScreenWaterfall.spanDocument.error": "在获取跨度文档时发生错误",
     "unifiedDocViewer.hideNullValues.switchLabel": "隐藏 null 字段",