Validate forced display size from settings

To avoid unexpected extreme large value that breaks bootup.
e.g. max=2147483647
     adb shell settings set global display_size_forced "$max,$max"
     adb reboot

Bug: 238420014
Test: atest DisplayWindowSettingsTests# \
      testDisplayWindowSettingsAppliedOnDisplayReady
Change-Id: If67f344cf55620b9c2fde2cfdbe20457021ff62e