This change adds the ability to configure outbound publishing of
extension state. Right now stuff is merely set up to store the
configuration and to register a global extension state callback. The
act of constructing the body and sending is not yet complete.

Configurable elements right now are a regex for filtering the context,
a regex for filtering the extension, and the body type to publish.

ASTERISK-25922 #close

Change-Id: Ia7e630136dfc355073c1cadff8ad394a08523d78