Add support for filling synoptic icons that point directly at an entity in ioc.yaml

[coretl]

It is correct that making DCM requires an entry in techui.yaml: you are making a new composite screen from multiple objects that match a prefix, along with a status PV.

However for a valve this is overkill, we don't want a composite screen or a status PV, we just want the icon to point to it.

I suggest there should be 2 sources of id for filling widgets:

• entries in techui.yaml like DCM register that id with the generated bob file path, and generated status pv
• entries in ioc.yaml files like BL19I-VA-VALVE-01 lookup if they have an entry in techui mapping, then insert their prefix, generated bob file path, and listed status pv

Acceptance Criteria

• You don't need to edit techui.yml when adding a new valve to a vacuum IOC, just add the icon to the synoptic and it will be filled by techui builder