BUG: Components / PVs not explicitly listed in the checkout can have cagets requested

[tangkong]

Expected Behavior

We should only attempt to access the data specified in the checkout

Current Behavior

For some devices, initializing the signal seems to try to access other PVs in the device.

Possible Solution

Be lazier?
grab the PV and make the signal explicitly? aka never try to instantiate the device when we load a checkout?

Steps to Reproduce (for bugs)

1. disable some parts (cameras on IM3K4)
2. ~tmoopr/atef/configure-file/common-components-partI-ATM-PF2K4.json

Context

Tong ran into this trying to use atef

For a checkout only containing Target PVs (motors/motion, moving target in and out)

Traceback

ERROR:ophyd:Exception occurred during callback <function PyepicsShimPV.get_all_metadata_callback.<locals>.get_metadata_thread at 0x7ff10ccb5550> (pvname='IM3K4:PPM:CAM:CamRepRate_RBV')
Traceback (most recent call last):
  File "/cds/group/pcds/pyps/conda/py39/envs/pcds-5.7.3/lib/python3.9/site-packages/ophyd/_dispatch.py", line 55, in run
    callback(*args, **kwargs)
  File "/cds/group/pcds/pyps/conda/py39/envs/pcds-5.7.3/lib/python3.9/site-packages/ophyd/_pyepics_shim.py", line 144, in get_metadata_thread
    md = self.get_all_metadata_blocking(timeout=timeout)
  File "/cds/group/pcds/pyps/conda/py39/envs/pcds-5.7.3/lib/python3.9/site-packages/ophyd/_pyepics_shim.py", line 137, in get_all_metadata_blocking
    self.get_ctrlvars(timeout=timeout)
  File "/cds/group/pcds/pyps/conda/py39/envs/pcds-5.7.3/lib/python3.9/site-packages/epics/pv.py", line 47, in wrapped
    return func(self, *args, **kwargs)
  File "/cds/group/pcds/pyps/conda/py39/envs/pcds-5.7.3/lib/python3.9/site-packages/epics/pv.py", line 734, in get_ctrlvars
    kwds = ca.get_ctrlvars(self.chid, timeout=timeout, warn=warn)
  File "/cds/group/pcds/pyps/conda/py39/envs/pcds-5.7.3/lib/python3.9/site-packages/epics/ca.py", line 635, in wrapper
    return fcn(*args, **kwds)
  File "/cds/group/pcds/pyps/conda/py39/envs/pcds-5.7.3/lib/python3.9/site-packages/epics/ca.py", line 1770, in get_ctrlvars
    metadata = get_with_metadata(chid, ftype=ftype, count=1, timeout=timeout,
  File "/cds/group/pcds/pyps/conda/py39/envs/pcds-5.7.3/lib/python3.9/site-packages/epics/ca.py", line 635, in wrapper
    return fcn(*args, **kwds)
  File "/cds/group/pcds/pyps/conda/py39/envs/pcds-5.7.3/lib/python3.9/site-packages/epics/ca.py", line 1390, in get_with_metadata
    return get_complete_with_metadata(chid, count=count, ftype=ftype,
  File "/cds/group/pcds/pyps/conda/py39/envs/pcds-5.7.3/lib/python3.9/site-packages/epics/ca.py", line 635, in wrapper
    return fcn(*args, **kwds)
  File "/cds/group/pcds/pyps/conda/py39/envs/pcds-5.7.3/lib/python3.9/site-packages/epics/ca.py", line 1531, in get_complete_with_metadata
    raise get_failure_reason
epics.ca.ChannelAccessGetFailure: Get failed; status code: 192

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