Fix markMentionsRead() for albums and action messages

[Azq2]

This PR fixes two related but independent issues.

1. For “system” messages (ActionMessage) the markMentionsRead() is never called.

2. For messages with albums (which actually consist of multiple messages), markMentionsRead() was called only for the first message, and not for all submessages.

Both these problems create problem, where unread mentions are just accumulated to infinity.

In my opinion, this is the most annoying bug in Telegram Web.

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