samples: video: capture: add crop/compose support

Demonstrate the crop/compose API by introducing 4 new
CONFIG options in order to define the crop area.
Moreover, if the selection API is available and if
the targetted size is different from the current crop
size, then try to apply a compose in order to reach
the targetted format size.

Signed-off-by: Alain Volmat <alain.volmat@foss.st.com>