Change representation of field selector occurrences
This issue is a sub-task of issue #19461 ("Remove AmbiguousFieldOcc").
The task is to:
- Change the names of the fields in type
FieldOcc
- Replace the use of
AmbiguousFieldOcc p
inHsRecFld
to useFieldOcc p
instead.
The change is spelled out in more detail in this note (section "Representation of field selector occurrences") in issue #19463 ("Refactor RecordUpd").