Rename the *Nat64Prefix to *Nat64PrefixFromDns.

This just a rename with no functional changes at all. It is
preparation for supporting getting the NAT64 prefix from the
RA.

Bug: 150648313
Test: covered by existing ConnectivityServiceTest and Nat464XlatTest
Change-Id: Ia9a09a708870827b1e4cf068f930fa9542dd116c
3 files changed
tree: 2df413169be730ba544b30861dd1aa88150d12a8
  1. core/
  2. services/
  3. tests/