Improve newly added code in MethodProposalInfo.resolveMember()

The PR https://github.com/eclipse-jdt/eclipse.jdt.ui/pull/2293 introduce new changes to the MethodProposalInfo.resolveMember() to select the record component field rather than the method. This works for the problem at hand, where we need the completion Javadoc to be fetched from the enclosing type. But this not perfect because other clients of this method might rather a null (for a method) than a record component. I am raising this so someone more knowledgeable in this area can take a look and see if this can be improved.

Start by reviewing PR 2293 and the current MethodProposalInfo.resolveMember() implementation. Trace the callers of this method, especially the record-component and completion-Javadoc cases, to determine whether selecting a record component or returning null is correct for each client. Done means the behavior is consistent for all callers without regressing the original completion case.

Written by the indexing model from the issue text.