Individually, these don't make much difference, but they add up
to a halving the time to save on my machine.

OTempFileService was spending a lot of time in PropertySetMixin doing
UNO reflection.
Re-implement the required property interfaces directly..

Change-Id: I9b6ef439d4c56eb40c1f5d636e3e5cb888d5d4ff
Reviewed-on: https://gerrit.libreoffice.org/70310
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>