Refactor virtual display properties initialization

Following the changes from the previous commit, the behavior is now
identical when mirroring the main display or using the SurfaceControl
API.

Factorize the code to perform the initialization in a single location.

Refs #5605 <https://github.com/Genymobile/scrcpy/issues/5605>
PR #5614 <https://github.com/Genymobile/scrcpy/pull/5614>