ENH: add `state_summary` to LightpathState, for showing select device signal information

Expected Behavior

From discussions on #157

I wonder if there is any metadata we could slide into the LightpathState dataclass to use in this space in an efficient way instead of the ad hoc "grab a few signals and make widgets".

Possible Solution

Just as an idea for a follow-up for what to do with the space, what if we extend like:

@dataclass
class LightpathState:
inserted: bool
removed: bool
transmission: float
output_branch: str
state_summary: str = ""
And then devices can provide text to lightpath to include in a label. Just a small idea, there are probably better ways to do this.

Context

#157

The commands widget was removed, and along with it the visibility of hinted signals. it might be nice to see these return, if performance issues can be solved. Implementing this should come with careful consideration of which components are being "woken up" and the ensuing performance impacts

Your Environment

pcds-5.4.2+lightpath pr's

Start by reading the discussion in #157 and locating the LightpathState dataclass and the removed commands widget. Determine whether a state_summary design can restore hinted signal visibility without waking too many components; done requires an agreed implementation and acceptable performance impact.