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?

package.json

@@ -7,6 +7,7 @@
       "packages/medusa-js",
       "packages/medusa-react",
       "packages/*",
+      "packages/admin-next/*",
       "packages/design-system/*",
       "packages/generated/*",
       "packages/oas/*",
@@ -38,6 +39,7 @@
     "eslint-plugin-prettier": "^4.2.1",
     "eslint-plugin-react": "^7.31.11",
     "eslint-plugin-react-hooks": "^4.6.0",
+    "eslint-plugin-react-refresh": "^0.4.5",
     "eslint-plugin-storybook": "^0.6.12",
     "eslint-plugin-unused-imports": "^2.0.0",
     "express": "^4.17.1",