Remove mails faster because users keep running out of quota

[link2xt]

For chatmail accounts the only options for "Delete Messages from Server" setting are "Automatic" and "At once after Download".

For multi-device setups users should use "Automatic", but they still keep running out of quota: https://support.delta.chat/t/warning-about-providers-storage-but-delete-from-server-is-enabled/3575

In default configuration messages are deleted after 20 days: https://github.com/deltachat/chatmail/blob/49907c78a36bbef1cf38d5f4b632e6d5306311e5/chatmaild/src/chatmaild/ini/chatmail.ini.f#L23-L24

A simple solution to keep users running out of quota is to delete large messages faster, e.g. after 7 days if the message is larger than 2 MB.

[thob]

I would also favor an option to set the automatic cleansing to like 5, 10, 15, 20 days – in my use case - notifications with images attached – I don't have large attachments but rather many messages containing smaller images.