1 - when CONTACTS_3PIDS_SYNC is set
the client looks up for ALL the known 3PIDs even if the linked contacts are not displayed
2 - when CONTACTS_3PIDS_SYNC is NOT set
the client looks up to the PIDS on demand i.e. the displayed contacts request their PIDs refresh.
The matrix IDs are retrieved in one time instead of getting them one by one
-> ConsoleEmail and ConsolePhoneNumber inherit of ConsoleContactField.
ConsoleContactField manages the matrix part (id + thumbnail download...)
-> the unknown room members are added into the contacts list.
Thus, it would easier to start a chat.