Add timeout for displaying 5G icon in SystemUI

SystemUI refer CarrierConfig timeout(Second) to show 5G icon gracefully

System UI will show the 5G icon and post message delay by config value
after the device connect to a 5G cell to make the UX better
System UI stop displaying 5G icon when below conditions matched
1. device disconnect from 5G cell
2. the timer is expired.

Fixes: 136636141
Bug: 136107473

Test: atest SystemUITests
Test: enable SystemUI Demo Mode, simulate mServiceState callback 5G
Test: adb shell am broadcast -a com.android.systemui.demo -e command network
      -e mobile show -e datatype 5g -e level 4
Test: adb shell am broadcast -a com.android.systemui.demo -e command network
      -e mobile show -e datatype 5g+ -e level 4

Design: go/sysui_5g_signal_timer

Change-Id: I5e723c3edf28d31725fa9d847ed3569a1c322739