Decrease the minimum depth of the depthimage_to_{mono, rgb} portmonitors

[xEnVrE]

Is your feature request related to a problem? Please describe.
We started using a new RealSense, namely the short-range camera D405, which can provide good depth maps for object as near as 7 cm to the camera.

As we tipically do, it is always useful to visualize the depth map in a yarpview using the depthimage_to_rgb portmonitor for debugging or just to quickly check that the camera is working as expected.

Unfortunately, the depthimage_to_rgb portmonitor is ignoring any value of depth lower than 0.2 m:

yarp/src/portmonitors/depthimage_to_rgb/DepthImage2.cpp

Line 52 in 51292e3

min = 0.2;

Describe the solution you'd like
Would it be possible to lower that value to something smaller, e.g. 0.01 m?

I can open a PR in case.

Additional context

This is an example of the depth visualization using the current configuration, min = 0.2:

while this is the same scene after changing min to 0.01:

cc @randaz81

[xEnVrE]

After talking with @Nicogene, we realized that the minimum is limited to 0.2 also for the depthimage_to_mono portmonitor:

yarp/src/portmonitors/depthimage_to_mono/DepthImage.cpp

Line 28 in 51292e3

min = 0.2;

[randaz81]

I think the best way to proceed is to add a run-time parameter to allow users to choose max and min

[randaz81]

Even if is a new feature, I think we can handle this as a bugfix. I'll thus proceed on the yarp 3.8 branch.

[xEnVrE]

cc @Arya07 @pestrstr