Is/fix/ring back

[isaacakakpo1]

ENGDESK-25481 - Ticket title

• Remote sdp was not being set for "telnyx_rtc.media" command. This is fixed in this pull request
• ReadMe has also been updated on how to use CallKit to report calls correctly, hence having a correct duration for calls

:older_man: :baby: Behaviors

Before changes

• Ringback tone was not playing

After changes

• Ringback tone works

TODO

Follow up with coretel why "telnyx_rtc.media" brings SDP whilst "telnyx_rtc.answer" does not. Is this the correct flow

✋ Manual testing

All Primary Features Work including changes