chore: move next admin packages to core repo (#5983)

**What**
- Move packages for `next` version of admin to core repo

**Other**
- Since this PR introduces packages that depend on Vite 5, it also introduces @types/node@^20. We have never had a direct dependency on the types package for Node, and as far as I can see that has resulted in us using the types from Node.js@8, as those are a dependency of one of our dependencies. With the introduction of @types/node@^20, two of our packages had TS errors because they were using the NodeJS.Timer type, which was deprecated in Node.js@14. We should add specific @types/node packages to all our packages, but I haven't done so in this PR to keep it as clean as possible.
- Q: @olivermrbl I've added the new packages to the ignore list for changeset, is this enough to prevent them from being published?

packages/admin-next/dashboard/src/app.tsx

@@ -0,0 +1,31 @@
+import { Toaster } from "@medusajs/ui"
+import { MedusaProvider } from "medusa-react"
+
+import { AuthProvider } from "./providers/auth-provider"
+import { RouterProvider } from "./providers/router-provider"
+import { ThemeProvider } from "./providers/theme-provider"
+
+import { queryClient } from "./lib/medusa"
+
+const BASE_URL =
+  import.meta.env.VITE_MEDUSA_ADMIN_BACKEND_URL || "http://localhost:9000"
+
+function App() {
+  return (
+    <MedusaProvider
+      baseUrl={BASE_URL}
+      queryClientProviderProps={{
+        client: queryClient,
+      }}
+    >
+      <ThemeProvider>
+        <AuthProvider>
+          <RouterProvider />
+          <Toaster />
+        </AuthProvider>
+      </ThemeProvider>
+    </MedusaProvider>
+  )
+}
+
+export default App