The OPTIONS support in PJSIP has organically grown, like many things in
Asterisk.  It has been tweaked, changed, and adapted based on situations
run into.  Unfortunately this has taken its toll.  Configuration file
based objects have poor performance and even dynamic ones aren't that
great.

This change scraps the existing code and starts fresh with new eyes.  It
leverages all of the APIs made available such as sorcery observers and
serializers to provide a better implementation.

1.  The state of contacts, AORs, and endpoints relevant to the qualify
process is maintained.  This state can be updated by external forces (such
as a device registering/unregistering) and also the reload process.  This
state also includes the association between endpoints and AORs.

2.  AORs are scheduled and not contacts.  This reduces the amount of work
spent juggling scheduled items.

3.  Manipulation of which AORs are being qualified and the endpoint states
all occur within a serializer to reduce the conflict that can occur with
multiple threads attempting to modify things.

4.  Operations regarding an AOR use a serializer specific to that AOR.

5.  AORs and endpoint state act as state compositors.  They take input
from lower level objects (contacts feed AORs, AORs feed endpoint state)
and determine if a sufficient enough change has occurred to be fed further
up the chain.

6.  Realtime is supported by using observers to know when a contact has
been registered.  If state does not exist for the associated AOR then it
is retrieved and becomes active as appropriate.

The end result of all of this is best shown with a configuration file of
3000 endpoints each with an AOR that has a static contact.  In the old
code it would take over a minute to load and use all 8 of my cores.  This
new code takes 2-3 seconds and barely touches the CPU even while dealing
with all of the OPTIONS requests.

ASTERISK-26806

Change-Id: I6a5ebbfca9001dfe933eaeac4d3babd8d2e6f082