fix(medusa,utils,test-utils,types,framework,dashboard,admin-vite-plugin,admin-bundler): Fix broken plugin dependencies in development server (#11720)

**What**
- Reworks how admin extensions are loaded from plugins.
- Reworks how extensions are managed internally in the dashboard project.

**Why**
- Previously we loaded extensions from plugins the same way we do for extension found in a users application. This being scanning the source code for possible extensions in `.medusa/server/src/admin`, and including any extensions that were discovered in the final virtual modules.
- This was causing issues with how Vite optimizes dependencies, and would lead to CJS/ESM issues. Not sure of the exact cause of this, but the issue was pinpointed to Vite not being able to register correctly which dependencies to optimize when they were loaded through the virtual module from a plugin in `node_modules`.

**What changed**
- To circumvent the above issue we have changed to a different strategy for loading extensions from plugins. The changes are the following:
  - We now build plugins slightly different, if a plugin has admin extensions we now build those to `.medusa/server/src/admin/index.mjs` and `.medusa/server/src/admin/index.js` for a ESM and CJS build.
  - When determining how to load extensions from a source we follow these rules:
    - If the source has a `medusa-plugin-options.json` or is the root application we determine that it is a `local` extension source, and load extensions as previously through a virtual module.
    - If it has neither of the above, but has a `./admin` export in its package.json then we determine that it is a `package` extension, and we update the entry point for the dashboard to import the package and pass its extensions a long to the dashboard manager.

**Changes required by plugin authors**
- The change has no breaking changes, but requires plugin authors to update the `package.json` of their plugins to also include a `./admin` export. It should look like this:

```json
{
  "name": "@medusajs/plugin",
  "version": "0.0.1",
  "description": "A starter for Medusa plugins.",
  "author": "Medusa (https://medusajs.com)",
  "license": "MIT",
  "files": [
    ".medusa/server"
  ],
  "exports": {
    "./package.json": "./package.json",
    "./workflows": "./.medusa/server/src/workflows/index.js",
    "./.medusa/server/src/modules/*": "./.medusa/server/src/modules/*/index.js",
    "./modules/*": "./.medusa/server/src/modules/*/index.js",
    "./providers/*": "./.medusa/server/src/providers/*/index.js",
    "./*": "./.medusa/server/src/*.js",
    "./admin": {
      "import": "./.medusa/server/src/admin/index.mjs",
      "require": "./.medusa/server/src/admin/index.js",
      "default": "./.medusa/server/src/admin/index.js"
    }
  },
}
```

packages/admin/admin-bundler/package.json

@@ -4,7 +4,7 @@
   "description": "Bundler for the Medusa admin dashboard.",
   "author": "Kasper Kristensen <kasper@medusajs.com>",
   "scripts": {
-    "build": "tsup && copyfiles -f ./src/index.html ./src/entry.tsx ./src/index.css ./dist"
+    "build": "tsup"
   },
   "main": "./dist/index.js",
   "types": "./dist/index.d.ts",
@@ -20,7 +20,6 @@
   "devDependencies": {
     "@medusajs/types": "2.6.1",
     "@types/compression": "^1.7.5",
-    "copyfiles": "^2.4.1",
     "express": "^4.21.0",
     "tsup": "^8.0.1",
     "typescript": "^5.3.3"
@@ -29,19 +28,16 @@
     "@medusajs/admin-shared": "2.6.1",
     "@medusajs/admin-vite-plugin": "2.6.1",
     "@medusajs/dashboard": "2.6.1",
-    "@rollup/plugin-node-resolve": "^16.0.0",
     "@vitejs/plugin-react": "^4.2.1",
     "autoprefixer": "^10.4.16",
     "compression": "^1.7.4",
     "express": "^4.21.0",
     "get-port": "^5.1.1",
     "glob": "^10.3.10",
+    "outdent": "^0.8.0",
     "postcss": "^8.4.32",
     "tailwindcss": "^3.3.6",
     "vite": "^5.4.14"
   },
-  "peerDependencies": {
-    "react-dom": "^18.0.0"
-  },
   "packageManager": "yarn@3.2.1"
 }