Improvements to the forked physics schemes

Shortly after the physics code was forked a list was collated of areas that should be improved to make it more LFRic friendly. This issue is to stop this information being lost - but it needs breaking down into actual issue in the future.

https://code.metoffice.gov.uk/trac/lfric_apps/wiki/Physics

Start by reading the physics improvement list on the linked LFRic wiki page and reviewing the forked physics code. The issue is complete only when the broad list has been broken into specific, actionable issues; no source files or tests are identified here.

Written by the indexing model from the issue text.