lfric2um: Adding ability to make output from lfric2um be a diagnostics fieldsfiles, not a dump fieldsfile.

[pdearnshaw]

Are there any linked Issues or Pull Requests?

No response

Brief description

lfric2um by default writes out a dump fieldsfile, and for the application of feeding data into VAR the fieldsfile needs to be of diagnostic type.

Further details of the issue.

No response