[pm/incremental] restore package loading progress on reboot

Also add loading progress in package dumpsys. Example:

$ adb shell dumpsys package
Package [com.supercell.clashroyale] (69009ab):
...
timeStamp=2021-01-27 13:16:01
firstInstallTime=2021-01-27 13:14:00
lastUpdateTime=2021-01-27 13:14:00
installerPackageName=com.android.vending
loadingProgress=57% <--- new
...

BUG: 178532628
BUG: 178528867
Test: manual with Clash Royale nugget installs
Change-Id: Ieedc92eee30de4c47d74a32018b8c92990c05328