Handle 410 Gone errors during Calendar sync

Summary:
According to https://developers.google.com/calendar/v3/errors, the server can return a 410 error if the syncToken or updatedMin is too old.
There is already code to preemptively request a full sync, but specifically for the "Contacts" calendar the server-side limit is much lower than usual, generating these errors and preventing sync.

Test Plan:

• Set last sync for "Contacts" calendar to five days ago.
• Observe 410 error being returned.
• Verify that a full sync is performed.

Reviewers: mlaurent, dvratil

Reviewed By: dvratil

Subscribers: lbeltrame, kde-pim

Tags: KDE PIM

Differential Revision: https://phabricator.kde.org/D27062