Support screen recording of multiple displays simultaneously.

Ensure layer stack assigned to each new virtual display is actually random (and different) by initializing via srand.
Assign unique display name to each new virtual display to better differentiate them.
Add --version flag to more easily parse version information than from --help.

Bug: 264688932
Flag: EXEMPT bug fix
Test: adb shell screenrecord --display-id VALID_DISPLAY_ID run twice in different terminals for different display ids
Change-Id: I7a3be9086cf91f98fbb88ad559e6a14e1513f250