feat(admin-bundler,admin-vite-plugin,medusa): Add support for loading Admin Extensions from plugins (#10869)

Should not be merged before https://github.com/medusajs/medusa/pull/10895

**What**
- Introduces a new `plugin` command to `admin-bundler`, currently not used anywhere but will be called from `medusa build:plugin`
- Discovers plugins with extensions and add passes the to `admin-vite-plugin`.
- Updates `admin-vite-plugin` so its able to read built admin extensions.

Resolves CMRC-830, CMRC-839

yarn.lock

@@ -5252,6 +5252,7 @@ __metadata:
     compression: ^1.7.4
     copyfiles: ^2.4.1
     express: ^4.21.0
+    glob: ^11.0.0
     postcss: ^8.4.32
     tailwindcss: ^3.3.6
     tsup: ^8.0.1