Refactor getPsiTargets method

[EgorkaKulikov]

Description

Current signature of the method is the following:

private fun getPsiTargets(e: AnActionEvent): Triple<Set<PsiClass>, Set<MemberInfo>, Boolean>?

Currently some absolutely unclear lines like this are used:

return Triple(setOf(srcClass), if (focusedMethod != null) setOf(focusedMethod) else emptySet(), true)

We should introduce some data class instead of Triple with meaningful field names, especially for the boolean flag.