Support WAC decoding in UMTS format

This add a decoder for WAC information. WAC is appended to the UMTS
cell broadcast message. The encoding is defined in ATIS-0700041.

Bug: 123096618
Test: build & manual test
Merged-In: I73dc22c27c2cfd47000ae65448fbc857ed9aa42f
Change-Id: I73dc22c27c2cfd47000ae65448fbc857ed9aa42f
(cherry picked from commit 14df7e3845369e7254e6aae13160c7e1caa1d28a)