script: Update indexeddb serialization (#38269)

- Dates are now serialized as f64s (like how firefox does it)
- Array buffers are serialized with structured cloning (this is not the
most correct/efficent way to serialize them, however it is currently
better than not supporting array buffers at all)
- Array types are still unimplemented.

Testing: WPT
Fixes: Some panicking

---------

Signed-off-by: Ashwin Naren <arihant2math@gmail.com>

components/shared/net/indexeddb_thread.rs

@@ -22,8 +22,7 @@ pub enum IndexedDBKeyType {
     Number(f64),
     String(String),
     Binary(Vec<u8>),
-    // FIXME:(arihant2math) Date should not be stored as a Vec<u8>
-    Date(Vec<u8>),
+    Date(f64),
     Array(Vec<IndexedDBKeyType>),
     // FIXME:(arihant2math) implment ArrayBuffer
 }