This moves a combination of tools::Time::GetSystemTicks(), canvas
ElapsedTime::getSystemTime() and the opencl timing implementation
into tools::Time::GetMonotonicTicks() as a monotonic microsecond
time source.

Change-Id: I5c9263540b8af55b2eeca6126e288129427f6e8e
Reviewed-on: https://gerrit.libreoffice.org/41991Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>