This is a major patch about refactoring all CallState/ConnectionState
over call and subclasses.
Please read carefully this message, it's about how to use the code.

First, this patch brings a central way to store both Call class states
members: only Call::setState() (and overloaded) has to be used now.

De-facto we use it to emit to the client the StateChange call signal,
and remove this emit spread over the code. A check is also made
to not emit it if the resulting client state doesn't change for
the given CallState/ConnectionState input pair.
So using this signal elsewhere is stricly forbidden now.

Then, a code cleanup has been made to had missing setState() calls
and check the global business logic about these states changes.
I hope this cleanup is correct (almost as good as before).

State transaction logic is, as before, checked by Call::validTransition.
Please modify it if state machine needs to be changed.
Also modify Call::getStateStr() to implements daemon->client
translated state machine.

Note: no API changes in this patch. Only behavior changes.

Refs #76646

Change-Id: Iecaedc2cad89b9afdc886f978bbf5f247cbe36bb
Signed-off-by: Guillaume Roguez <guillaume.roguez@savoirfairelinux.com>