indexeddb: Implement autoincremented keys and report autoincrementedness properly through DOM interface (#38723)

Autoincrementedness was previously being reported as always false. This
PR makes the state become queried from the backend, as the spec
specifies. Additionally this PR ensures the backend correctly handles an
object store which autoincrements.

Testing: WPT
Fixes: None

---------

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

components/net/indexeddb/engines/sqlite/create.rs

@@ -22,7 +22,7 @@ create table object_store (
     name           varchar               not null
         unique,
     key_path       varbinary_blob,
-    auto_increment boolean default FALSE not null
+    auto_increment integer default FALSE not null
 );"#;
     conn.execute(OBJECT_STORE, [])?;