MLECO-5340: Initial VSI support

Adding basic Virtual Streaming Interface (VSI) support for HAL camera
interface alongside the default `hal_camera_static_images` library.
Platform drivers for MPS3 and MPS4 targets can enable use of this
library based on a new CMake configuration parameter `FVP_VSI_ENABLED`
By default this is turned OFF.

This will allow all vision-based examples to stream images from camera
connected to a host machine. Although VSI could also be used to read
frames from an input video file on disk (on host), provision for this
has not been added.

Change-Id: I56bd2fa07742170b146cae51e6ff10ee1900a63f
Signed-off-by: Kshitij Sisodia <kshitij.sisodia@arm.com>