Improve performance of profile reporting

Discovered during the investigation for MB-61027.

MB-21959 added variable duration formatting.  To achieve this we have to reprocess the profile but are doing it unnecessarily when the duration format isn't changing.  Furthermore the approach of conversion to a simple objectValue for processing before converting back to the output profile is wasteful and we can achieve better performance if we skip this and work on the output profile directly - in some cases.

This was highlighted as an issue in MB-61027 only really because of the ultra-short statement duration meant this overhead was a higher proportion of the request processing time.