Migrate - Data Backup

Nov 1, 2020

# Compatibility fixes for Android 11
# Add Message center to display important announcements.
# Migrate helper now allows to retry failed apk installs
# Add a "Migrate flasher only" backup option
# Save app icons as png files
# Show number of apps selected for backup in Extra backups screen
# Keep screen on when calculating backup size
# Save last state of selection in extras
# Don't remount /data partition in system test
# Many under the hood changes