Sysui/WifiTracker: Changes to support late starting wifi service

Wifi service may not be up when WifiTracker, Sysui is initialized. So,
move some of the wifi operations to later stage in the bootup sequence.

1) Wifi service may not be up when WifiTracker is initialized, use the
underlying wifi verbose logging global setting directly to set the static
verbose logging flag.
2) Use the boot completed broadcast to register wifi traffic state
change callbacks in Sysui.
3) Register for softap callbacks only when sysui is active (not at
bootup).

Bug: 113174748
Test: No sysui crash at bootup with the wifi stack apk
Change-Id: I25182875922ea6acf2b7c0af6460ada311b6827b
Merged-In: I25182875922ea6acf2b7c0af6460ada311b6827b