autotest: cellular: Add network_3GIdentifiers.

BUG=chromium:234713
TEST=Run against LTE, GSM and CDMA modems, run control.pseudomodem.

Change-Id: I2fb5094dadefe148da13738d2a2362f8943212c2
Reviewed-on: https://gerrit.chromium.org/gerrit/49658
Reviewed-by: Thieu Le <thieule@chromium.org>
Tested-by: Thieu Le <thieule@chromium.org>
Reviewed-by: Ben Chan <benchan@chromium.org>
Commit-Queue: Thieu Le <thieule@chromium.org>
6 files changed