libcamera: pipeline: Add a simple pipeline handler

This new pipeline handler aims at supporting any simple device without
requiring any device-specific code. Simple devices are currently defined
as a graph made of one or multiple camera sensors and a single video
node, with each sensor connected to the video node through a linear
pipeline.

The simple pipeline handler will automatically parse the media graph,
enumerate sensors, build supported stream configurations, and configure
the pipeline, without any device-specific knowledge. It doesn't support
configuration of any processing in the pipeline at the moment, but may
be extended to support simple processing such as format conversion or
scaling in the future.

The only device-specific information in the pipeline handler is the list
of supported drivers, required for device matching. We may be able to
remove this in the future by matching with the simple pipeline handler
as a last resort option, after all other pipeline handlers have been
tried.

Signed-off-by: Martijn Braam <martijn@brixit.nl>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Andrey Konovalov <andrey.konovalov@linaro.org>

meson_options.txt

@@ -14,7 +14,7 @@ option('gstreamer',
 
 option('pipelines',
         type : 'array',
-        choices : ['ipu3', 'rkisp1', 'uvcvideo', 'vimc'],
+        choices : ['ipu3', 'rkisp1', 'simple', 'uvcvideo', 'vimc'],
         description : 'Select which pipeline handlers to include')
 
 option('test',