Adds getChannelNumber() to CellIdentity.
Creates a static utility class to calculate the duplex mode from an
EARFCN.
Bug: 73728783
Test: runtest frameworks-telephony
Change-Id: I5b5c4efa7e17594ce9397cf65e129147affe96bd
Merged-In: I5b5c4efa7e17594ce9397cf65e129147affe96bd
(cherry picked from commit a483ce3bfd)