feat(dashboard): ability to locate new admin route under existing route (#10587)

This PR add ability to locate new admin route under existing route in sidebar.

For example, new route Brands
![image](https://github.com/user-attachments/assets/1b297fb0-296c-4e94-a4cb-f84f4c676c53)
![image](https://github.com/user-attachments/assets/80336909-1c0a-49c9-b8e1-3b1137ae2e48)

https://github.com/user-attachments/assets/b46b1813-e92e-4b67-84a1-84660023ac7c

packages/admin/dashboard/src/components/layout/main-layout/main-layout.tsx

@@ -284,6 +284,19 @@ const Searchbar = () => {
 const CoreRouteSection = () => {
   const coreRoutes = useCoreRoutes()
 
+  const { getMenu } = useDashboardExtension()
+
+  const menuItems = getMenu("coreExtensions")
+
+  menuItems.forEach((item) => {
+    if (item.nested) {
+      const route = coreRoutes.find((route) => route.to === item.nested)
+      if (route) {
+        route.items?.push(item)
+      }
+    }
+  })
+
   return (
     <nav className="flex flex-col gap-y-1 py-3">
       <Searchbar />
@@ -298,7 +311,7 @@ const ExtensionRouteSection = () => {
   const { t } = useTranslation()
   const { getMenu } = useDashboardExtension()
 
-  const menuItems = getMenu("coreExtensions")
+  const menuItems = getMenu("coreExtensions").filter((item) => !item.nested)
 
   if (!menuItems.length) {
     return null

packages/admin/dashboard/src/components/layout/nav-item/nav-item.tsx

@@ -26,6 +26,7 @@ export type INavItem = {
   items?: NestedItemProps[]
   type?: ItemType
   from?: string
+  nested?: string
 }
 
 const BASE_NAV_LINK_CLASSES =