Looks the name up and returns the structure destination its value carries, if any.
public PdfExplicitDestination? ResolveStructureDestination()
SD entry of the named destination's dictionary value as a destination; null when the destination
is remote, the name does not resolve, its value is an array, or the dictionary has no usable SD.
ISO 32000-2 §12.3.2.4: a named destination's value may be a dictionary with a D entry that "may optionally contain an
SD entry as defined in Table 201", which should take precedence over D (§12.3.2.3). An SD that is not an array
is reported (DestinationInvalid) and read as absent.