Return default device settings from ActivityThread for no override

If there are no settings overrides for a virtual device, ActivityThread
should return the cached value of the default device settings for any
virtual device id.

Test: atest VirtualDeviceViewConfigurationTest
Fixes: 424441365
Flag: android.companion.virtualdevice.flags.device_aware_settings_override
Change-Id: I4d2678caa141e3202722693b94886c8ad9534c8c