How to incorporate "descriptions" in VTypes

[shroffk]

The VTypes encapsulate the description as part of the display. This is not correct in my opinion.
As this PR discussion shows
ControlSystemStudio/phoebus#3228

There are various value types like boolean, enum, string which might not justify have all the elements of "display" associated with them but they certainly can have a description.

Currently, it is not possible to only add a description without adding the entire display. We should fix the VTypes such that description and display are treated seperately.

[kasemir]

Issue:
Every EPICS record has a DESC field. Channel access does not provide access to it via any of the DBR_.. structures, need to create a separate channel to xxx.DESC, which will fail if "xxx" is not a record on an IOC but a PCAS-served channel.
PVAccess added a description to its "display" information, but that display info is really meant for numeric data, containing units, display, control and alarm ranges. There is no normative type that reports the description for enumerated or string records.

Update normative types and QSRV to report description for enumerated or string records?
Add description to basic VType? Or description interface that'll be in display info, enum label info?