[App Menu] Fix action button popover reposition (#272011)

## Summary

This PR fixes a bug where for some reason, in classic mode (works fine
in solution mode), the primary action item with a popover would have the
popover rendered to the left instead of `downRight`.

**Before:**

<img width="347" height="161" alt="Screenshot 2026-05-30 at 01 17 20"
src="https://github.com/user-attachments/assets/96787637-da8b-4dca-b53a-3144f1441f04"
/>

After:

<img width="247" height="194" alt="Screenshot 2026-05-30 at 00 34 33"
src="https://github.com/user-attachments/assets/3f9fc391-6fcc-4af8-81ff-c786ba3b0ccf"
/>

Author: kowalczyk-krzysztof

src/core/packages/chrome/app-menu/core-chrome-app-menu-components/src/components/app_menu_action_button.tsx

@@ -177,6 +177,7 @@ export const AppMenuActionButton = (props: AppMenuActionButtonProps) => {
         popoverWidth={popoverWidth}
         popoverTestId={popoverTestId}
         anchorPosition="downRight"
+        repositionToCrossAxis={false}
         onClose={onPopoverClose}
         onCloseOverflowButton={onCloseOverflowButton}
       />
@@ -195,6 +196,7 @@ export const AppMenuActionButton = (props: AppMenuActionButtonProps) => {
         popoverWidth={popoverWidth}
         popoverTestId={popoverTestId}
         anchorPosition="downRight"
+        repositionToCrossAxis={false}
         onClose={onPopoverClose}
         onCloseOverflowButton={onCloseOverflowButton}
       />

src/core/packages/chrome/app-menu/core-chrome-app-menu-components/src/components/app_menu_popover.tsx

@@ -30,6 +30,7 @@ interface AppMenuContextMenuProps {
   switchConfig?: AppMenuSwitch;
   popoverTestId?: string;
   anchorPosition?: PopoverAnchorPosition;
+  repositionToCrossAxis?: boolean;
   onClose: () => void;
   onCloseOverflowButton?: () => void;
 }
@@ -47,6 +48,7 @@ export const AppMenuPopover = ({
   switchConfig,
   popoverTestId = 'app-menu-popover',
   anchorPosition = 'downLeft',
+  repositionToCrossAxis,
   onClose,
   onCloseOverflowButton,
 }: AppMenuContextMenuProps) => {
@@ -100,6 +102,7 @@ export const AppMenuPopover = ({
       hasArrow={false}
       anchorPosition={anchorPosition}
       aria-label={title || content}
+      repositionToCrossAxis={repositionToCrossAxis}
     >
       <EuiContextMenu initialPanelId={0} panels={panels} css={{ minWidth: 180 }} />
     </EuiPopover>