UKESM-fast

UKESM-hybrid could be made faster by including elements from the UKESM-fast project

• UKESM-fast will aim to create a much faster version of UKESM1 by
  • Increasing timestep, maybe 20 mins -> 45mins/1hr
  • Reducing vertical levels, maybe 85 -> 38
  • Reducing frequency of full chemistry, maybe 1hr -> 2/3 hrs
  • ... and there's more
• Work on UKESM-fast will follow when UKESM1-hybrid is largely completed