[Provider Model] 1. Use the original string for Calls & SMS 2. Set preferred status in Call & SMS

1.
UX modify the string in document

Dual SIMs:
    Calls & SMS
    Google Fi (preferred), AT&T

    Calls & SMS
    Google Fi (preferred for calls), AT&T (preferred for SMS)

    Calls & SMS
    Google Fi (Temporarily unavailable), AT&T

Single SIM:
    Calls & SMS
    Temporarily unavailable

2.
UX: https://screenshot.googleplex.com/B9BETTwRoa4mfds.png
Implementation: https://screenshot.googleplex.com/4vxMLBynwdTvhEs.png

Bug: 178916743
Test: make
Change-Id: I444eb0e3361707764dae18b9fa942c7f7a80a2c6