feat(admin-sdk,admin-bundler,admin-shared,medusa): Restructure admin packages (#8988)

**What**
- Renames /admin-next -> /admin
- Renames @medusajs/admin-sdk -> @medusajs/admin-bundler
- Creates a new package called @medusajs/admin-sdk that will hold all tooling relevant to creating admin extensions. This is currently `defineRouteConfig` and `defineWidgetConfig`, but will eventually also export methods for adding custom fields, register translation, etc. 
  - cc: @shahednasser we should update the examples in the docs so these functions are imported from `@medusajs/admin-sdk`. People will also need to install the package in their project, as it's no longer a transient dependency.
  - cc: @olivermrbl we might want to publish a changelog when this is merged, as it is a breaking change, and will require people to import the `defineXConfig` from the new package instead of `@medusajs/admin-shared`.
- Updates CODEOWNERS so /admin packages does not require a review from the UI team.

packages/admin/dashboard/src/hooks/use-handle-table-scroll.tsx

@@ -0,0 +1,24 @@
+import { useRef, useState } from "react"
+
+export const useHandleTableScroll = () => {
+  const tableContainerRef = useRef<HTMLDivElement>(null)
+
+  // Listen for if the table container that has overflow-y: auto is scrolled, and if true set some state
+  const [isScrolled, setIsScrolled] = useState(false)
+
+  const handleScroll = () => {
+    if (tableContainerRef.current) {
+      setIsScrolled(
+        tableContainerRef.current.scrollTop > 0 &&
+          tableContainerRef.current.scrollTop <
+            tableContainerRef.current.scrollHeight
+      )
+    }
+  }
+
+  return {
+    tableContainerRef,
+    isScrolled,
+    handleScroll,
+  }
+}