Group notifications (by tv shows or send them in batches)

Right now when few tens/hundreds of episodes are added, you could get same number of notifications * chosen languages, which is quite a lot (I use Telegram, but I guess it could be said about everything, especially email).

Tautulli solves that by grouping shows by season added, but this way may be lacking some info in case of subtitles, but still viable as an option. Another option would be to concat the notifications instead of sending them out immediately, and then send them all in one message once per N hours or something. But that requires knowing the limits of every agent to split when needed (Telegram max length is 4096 chars)

Also, when talking about notifications, some filters could be useful For example when using sonarr/radarr tags, or creating own tags, or just putting a list of titles to be notified about, or a list of languages that need notification.

https://github.com/morpheus65535/bazarr/issues/270