res_pjsip_exten_state: Use the extension for publishing to.

res_pjsip_exten_state: Use the extension for publishing to.

This change uses the newly added multi-user support for
outbound publish to publish to the specific user that an
extension state change is for.

This also extends the res_pjsip_outbound_publish support
to include the user specific From and To URI information in
the outbound publishing of extension state. Since the URI
is used when constructing the body it is important to ensure
that the correct local and remote URIs are used.

Finally the max string growths for the dialog-info+xml
body generator has been increased as through testing it has
proven to be too conservative.

ASTERISK-25965

Change-Id: I668fdf697b1e171d4c7e6f282b2e1590f8356ca1