am 96764812: cherrypick Change-Id: I3c2a7ea731d2fc3c0e2372e2f1a06ed659a6539f docs: move the SIP guide into guide/network/

* commit '967648121d3857b808941848203dfa44229781d7':
  cherrypick Change-Id: I3c2a7ea731d2fc3c0e2372e2f1a06ed659a6539f docs: move the SIP guide into guide/network/