add camera_info input for the pinhole model

Nothing in a dataflow carries fx, fy, cx and cy except the camera, and every
pixel of a depth map needs them to become a 3D point. The node now accepts
them so whatever computes that next has them to hand.

They are read from two places because dora-zed publishes them twice: the
camera_info message, and the metadata of every frame. The per-frame copy is
not redundant -- camera_info goes out once per camera session, so a viewer
started after the camera would otherwise never see it, and reading frame
metadata means wiring the input is optional even for a camera that publishes
it.

A nine-element row-major K is accepted alongside the compact [fx, fy, cx, cy],
since that is how ROS spells the same model in sensor_msgs/CameraInfo.

The model is drawn under the caption rather than only stored. A depth map read
through the wrong intrinsics looks entirely plausible, and this is where that
becomes visible.

as_float32 moves to a payload module: camera_info arrives as a raw byte slice
for the same reason the depth map does, and the reinterpretation is now shared
rather than written twice.

Verified with dora-cli 1.0.1: validate passes with four contracts injected on
each side, the dataflow runs to a clean exit, and a composed frame was
rendered and inspected with the model drawn on it.

examples/dora-node.yml

@@ -12,7 +12,7 @@
 apiVersion: 1
 name: source
 namespace: liria
-description: Synthetic image, depth, bbox and text source for the dora-image-view example
+description: Synthetic image, depth, camera_info, bbox and text source for the dora-image-view example
 categories: [debug]
 keywords: [example, test, synthetic]
 
@@ -39,6 +39,11 @@ outputs:
   text:
     type: std/core/v1/String
     description: A fixed caption.
+  camera_info:
+    type: std/core/v1/Float32
+    description: >-
+      [fx, fy, cx, cy] for the frames above. Published once, on the first tick,
+      the way a real camera publishes it once per session.
   depth:
     type: std/core/v1/Float32
     description: >-