Replace Contacts picker by the Element iOS one

[phloux]

Currently, Element iOS and Tchap iOS have not the same contacts picker.
We use a specific one for Tchap, but we should use the Element one.

And we also have a duplicate dataSource for this. So we need to remove the Tchap specific dataSource currently called ContactsDataSourceTchap

[giomfo]

This picker is used in multiple cases:

• start a new DM

• invite a new room member

• The Element picker displays a tile to prompt the user to access the contact book, we will hide this tile in Tchap in all cases

• Hide the contact book settings from the application settings

• in case of a new DM, we will hide in Tchap the "invite friends.." button

• in case of the invite of new room member, we will keep display the option "share invite link". The handling of this option should be improved in Element-iOS see