Switch indexeddb backend to sqlite and improve IPC messaging (#38187)

- Use sqlite instead of heed. (one indexed database = one sqlite
database)
- Implement the backend for indexes
- Use keyranges where needed (as specified by the spec)
- Implement `getKey`
- Fix channel error messaging (led to a bunch of changes to how async
requests are handled)

Note: `components/net/indexeddb/engines/sqlite/serialize.rs` is unused;
I can delete it if needed.

Testing: Switching to sqlite eliminated many panics (exposing some new
failures).
Fixes: #38040

---------

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

components/script/dom/idbopendbrequest.rs

@@ -7,7 +7,7 @@ use ipc_channel::router::ROUTER;
 use js::jsval::UndefinedValue;
 use js::rust::HandleValue;
 use net_traits::IpcSend;
-use net_traits::indexeddb_thread::{IndexedDBThreadMsg, SyncOperation};
+use net_traits::indexeddb_thread::{BackendResult, IndexedDBThreadMsg, SyncOperation};
 use profile_traits::ipc;
 use script_bindings::conversions::SafeToJSValConvertible;
 use stylo_atoms::Atom;
@@ -84,7 +84,7 @@ impl OpenRequestListener {
         }
     }
 
-    fn handle_delete_db(&self, result: Result<(), ()>, can_gc: CanGc) {
+    fn handle_delete_db(&self, result: BackendResult<()>, can_gc: CanGc) {
         let open_request = self.open_request.root();
         let global = open_request.global();
         open_request.idbrequest.set_ready_state_done();
@@ -108,7 +108,7 @@ impl OpenRequestListener {
                 event.fire(open_request.upcast(), can_gc);
             },
             Err(_e) => {
-                // FIXME(rasviitanen) Set the error of request to the
+                // FIXME(arihant2math) Set the error of request to the
                 // appropriate error
 
                 let event = Event::new(