fix(ui,types): Add Metadata form for collection (#11300)

**What**
- Adds missing Metadata form for collections
- Fixes type of metadata in update payload
- Fixes an issue where deleting the last row of a metadata form would prevent adding new ones.

Resolves SUP-784

.changeset/blue-files-work.md

@@ -0,0 +1,6 @@
+---
+"@medusajs/dashboard": patch
+"@medusajs/types": patch
+---
+
+fix(ui,types): Add Metadata form for collection