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/admin-bundler/src/api/bundle.ts

@@ -0,0 +1,46 @@
+import { readFileSync } from "fs"
+import glob from "glob"
+import { relative, resolve } from "path"
+import { build as command } from "vite"
+
+type BundleArgs = {
+  root?: string | undefined
+  watch?: boolean | undefined
+}
+
+export async function bundle({ watch, root }: BundleArgs) {
+  const resolvedRoot = root
+    ? resolve(process.cwd(), root)
+    : resolve(process.cwd(), "src", "admin")
+
+  const files = glob.sync(`${resolvedRoot}/**/*.{ts,tsx,js,jsx}`)
+
+  const input: Record<string, string> = {}
+  for (const file of files) {
+    const relativePath = relative(resolvedRoot, file)
+    input[relativePath] = file
+  }
+
+  const packageJson = JSON.parse(
+    readFileSync(resolve(process.cwd(), "package.json"), "utf-8")
+  )
+  const external = [
+    ...Object.keys(packageJson.dependencies),
+    "@medusajs/ui",
+    "@medusajs/ui-preset",
+    "react",
+    "react-dom",
+    "react-router-dom",
+    "react-hook-form",
+  ]
+
+  await command({
+    build: {
+      watch: watch ? {} : undefined,
+      rollupOptions: {
+        input: input,
+        external: external,
+      },
+    },
+  })
+}