Optimize hints for compound devices

[Cathyhjj]

Describe the bug

For example, when using line scan, and scanned the KB slits center, in the run browser, the KB slits center is not hinted

[canismarko]

I think we want to make the readback signal be hinted on the SlitsPositioner()

[Cathyhjj]

another issue is that, monochromator-pitch2/offset/vert... are also in the hinted detector list. Should we consider removing them from the hinted detectors?

[Cathyhjj]

[canismarko]

Should we consider removing them from the hinted detectors?

I agree that they don't really need to be hinted when reading the monochromator.

Other thoughts:

1. each motor's readback signal should be hinted if reading the motor itself, like when scanning that motor.
2. Those motors should still be included when reading the monochromator (just not hinted)
3. Those motors should be included when reading the configuration.

Does that sound right?

If we want to achieve all those goals, then I think we need to explicitly declare all the hinted, config, and readable signals for the monochromator device.

[canismarko]

It's probably a good time to make sure all the devices have the rights hints.