Supports hot plug video devices

This change implements a logic to support hot plug video devices, such
as USB webcam, by handling uevent message from kernel.

And, EVS app is modified to retrieve a camera list from EVS
manager, not its configuration file.

Bug: 126780934
Test: Build and test on Hawk
Change-Id: I1fe33e58020edfa752148cafba052acf0e4c29d5
Signed-off-by: Changyeon Jo <changyeon@google.com>
8 files changed