[Telephony Debug Menu] Add Link Capacity Estimate

Register for the Link capacity estimate for the
cellular default data connection and report it
in the debug menu.

Bug: 78791811
Test: manual
Merged-In: I73d945dfa192873936107902e0de6d58fc69059b
Change-Id: I73d945dfa192873936107902e0de6d58fc69059b
(cherry picked from commit f10ea32d)