res_pjsip: Add 'user_eq_phone' option to add a 'user=phone' parameter when applicable.

res_pjsip: Add 'user_eq_phone' option to add a 'user=phone' parameter when applicable.

Note that this is a backport of r425804 from trunk.

This change adds a configuration option which adds a 'user=phone' parameter if the user
portion of the request URI or the From URI is determined to be a number.

Review: https://reviewboard.asterisk.org/r/4073/

ASTERISK-24643 #close

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Merged revisions 430083 from http://svn.asterisk.org/svn/asterisk/branches/13

git-svn-id: https://origsvn.digium.com/svn/asterisk/certified/branches/13.1@430085 65c4cc65-6c06-0410-ace0-fbb531ad65f3