Trends diagnostics may not be scientifically correct in RK3

Context

• Branches impacted: main, branch_5.0

Analysis

Although functional (i.e. can be run without crashing), the trends diagnostics are not necessarily scientifically valid.

One example- trd_dyn is only called with jpdyn_spg in dyn_spg, which is only called when using MLF. This presumably means this component of the trends is not output when using RK3.

Fix

A scientific review of the TRD code is needed, but this is not a trivial task.

For the time being, if the trends diagnostics are activated then disable them and print a warning:

  ===>>> : W A R N I N G
 
          ===============
 
 The trends diagnostics are disabled, pending a full review.

In branch_5.0 this is implemented for both MLF and RK3.