Add links and usage context for telephony strings.

These strings are "strung" together in Telephony for various service
enable/disable operations.  To make it easier for the translation team to
see the context of where these strings are used, adding in links between
the various strings that depend on one another.

Test: Docs only change.
Bug: 205143948
Change-Id: I38ad5f15314fbc35b1bd10ca430a4454de1906fc