Make HID keyboard and mouse optional in OTG mode

Allow to only enable HID keyboard or HID mouse:

    scrcpy --otg -K   # keyboard only
    scrcpy --otg -M   # mouse only
    scrcpy --otg -KM  # keyboard and mouse
    scrcpy --otg      # keyboard and mouse

PR #2974 <https://github.com/Genymobile/scrcpy/pull/2974>