Enforce min installable target sdk version

This change will block the installation (but not the execution)
of apps that do not meet the minimum target sdk version.

The intention is to improve security and privacy by blocking low
target sdk apps as malware can target older sdk versions to avoid
the enforcement of new API behavior.

This change is fenced off by a feature flag. The plan is to
progressively ramp up the min_installable_target_sdk version
up to version 23 for Android U.

Bug: 237321649
Test: adb shell device_config put package_manager_service MinInstallableTargetSdk__install_block_enabled true
Test: adb shell device_config put package_manager_service MinInstallableTargetSdk__min_installable_target_sdk 5
Test: adb install com.senecacreeksoftware.simpletip-3.apk (this app uses
target sdk 4)
Test: adb shell device_config put package_manager_service
MinInstallableTargetSdk__min_installable_target_sdk 6
Test: adb install com.senecacreeksoftware.simpletip-3.apk
Test: adb shell device_config put package_manager_service
MinInstallableTargetSdk__min_installable_target_sdk 23
Test: Attempted side load install via files app
Test: Attempted install from Play Store of low target sdk app

Change-Id: Id86c65d088b62b0a9b36734c14fbf919fa458e32