doFetchModBlockedList is blocking the ui thread.
Duplicate data in `doFetchModBlockedList::blockListsPerChannel` to about 1000. The tab is dead when function hits, about 4s after reload.
- Yield occasionally using the `setTimeout` method.
- Doing a chunk size of 1 for now so we don't have to yield the inner loop as well (seems good enough). This is just based on a relatively large blocklist size.
- Can't do `await` in a callback, so must change the `forEach` to a `for`.
