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>

tests/wpt/meta/html/anonymous-iframe/indexeddb.tentative.https.window.js.ini

@@ -1,4 +1,4 @@
 [indexeddb.tentative.https.window.html]
-  expected: CRASH
+  expected: TIMEOUT
   [indexeddb]
     expected: TIMEOUT