EventHub messages ignoring both checkpoint and StreamSequenceToken

We've recently noticed that what is happening on #2935 is happening again. Regardless of the checkpoint being write, all the streams seems to always start from the beginning of the EH causing duplicated messages to arrive on the grain.

Both @jiilaa and myself had the same issues as on that issue.

In my case, I tried to create the following measures to avoid that:

1. Save every single `StreamSequenceToken` to the grain state as soon as I have the message processed.
2. At `OnActivateAsync()`, pass the token to `SubscribeAsync()` (implicit subscription stream).

@benjaminpetit can you have a look on those? I've discussed with @ReubenBond earlier Today and it seems something that is affect again all users of EH.

Thanks!