Assumption of _write_pv may not be accurate for all signal types

[klauer]

(More details to follow; and hopefully a fix!)

Current Behavior

Traceback (most recent call last):
  File "/cds/group/pcds/pyps/conda/py39/envs/pcds-5.1.1/lib/python3.9/site-packages/typhos/utils.py", line 1319, in wrapped
    link_signal_to_widget(signal, widget)
  File "/cds/group/pcds/pyps/conda/py39/envs/pcds-5.1.1/lib/python3.9/site-packages/typhos/utils.py", line 1274, in link_signal_to_widget
    widget.channel = channel_from_signal(signal, read=read)
  File "/cds/group/pcds/pyps/conda/py39/envs/pcds-5.1.1/lib/python3.9/site-packages/typhos/utils.py", line 161, in channel_from_signal
    return channel_name(signal._write_pv.pvname)
AttributeError: 'PytmcSignalRO' object has no attribute '_write_pv'

Possible Solution

Steps to Reproduce (for bugs)

1. 2. 3.

Context

Your Environment