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/vite-plugin-extension/package.json

@@ -0,0 +1,39 @@
+{
+  "name": "@medusajs/vite-plugin-extension",
+  "version": "0.0.0",
+  "main": "dist/index.js",
+  "types": "dist/index.d.ts",
+  "module": "dist/index.mjs",
+  "exports": {
+    ".": {
+      "import": "./dist/index.mjs",
+      "require": "./dist/index.js"
+    }
+  },
+  "files": [
+    "dist"
+  ],
+  "scripts": {
+    "build": "tsup"
+  },
+  "devDependencies": {
+    "@babel/types": "7.22.5",
+    "@medusajs/admin-shared": "*",
+    "@types/babel__traverse": "7.20.5",
+    "@types/node": "^20.10.4",
+    "tsup": "8.0.1",
+    "typescript": "5.3.3",
+    "vite": "5.0.10"
+  },
+  "peerDependencies": {
+    "vite": "^5.0.0"
+  },
+  "dependencies": {
+    "@babel/parser": "7.23.5",
+    "@babel/traverse": "7.23.5",
+    "chokidar": "3.5.3",
+    "fdir": "6.1.1",
+    "magic-string": "0.30.5"
+  },
+  "packageManager": "yarn@3.2.1"
+}