Provide detail on problem searches in problems guidance

[martinhillyard]

There is details regarding the return of problems records in various parts of the specification to provide detail on search behaviour and returning relating problems and populating the primary and secondary list.

There is no reference to this in the problems guidance though to hepl the user navigate the detail across the specification. Users have requested clarifications. Add detail to the problems guidance to describe the expected search behaviour and reference the additional materials in other sections to support user understanding and hopefully add clarity.

This is just to clarify the original requirements and does not impact #1070 which considers a future enhancement to return all linked problems when any one of those matches a search parameter.