Do not send IncomingCall events for contact requests and blocked contacts

[link2xt]

Currently with core 2.20.0 and 2.21.0 IncomingCall event is sent for contact requests and blocked contacts.

With UIs that show notifications and ring on such event this means blocked contacts can call users:
deltachat/deltachat-android#3952

IncomingCall event should not be sent unless the contact is accepted.