feat: Limit the size of aggregated WebXDC update to 100 KiB (#4825)

[iequidoo]

See commit messages. Close #4825

[link2xt]

Also don't send any updates together with the WebXDC instance to not complicate the code, the only downside is sending one message more when resending or forwarding WebXDC instances.

What happens in case of message draft where sender wants to set up everything (e.g. a poll) before sending the message out? I think this should always be a single message so we are sure that second message is not lost.

In case of forwarding we don't send updates anyway.

[iequidoo]

What happens in case of message draft where sender wants to set up everything (e.g. a poll) before sending the message out? I think this should always be a single message so we are sure that second message is not lost.

Makes sense, i'll change this back. But in case of resending it's easier not to send any updates together with the instance, but in separate messages of limited size.

In case of forwarding we don't send updates anyway.

True, and this is not changed, will fix the commit message.

EDIT: Done