Port ICAO convective cloud height and undilute CAPE diagnostics from UM to LFRic

### Are there any linked Issues or Pull Requests?

_No response_

### Brief description

The UM outputs the convective cloud base and top height diagnostics converted to International Civil Aviation Organisation "standard heights"; these are output by the operational suite and used by downstream products (presumably used by airports and airlines).

The UM also outputs an undilute CAPE diagnostic which is not yet available in LFRic but is output by the current OS.

We need to port the code which calculates these diagnostics to LFRic, so we can keep outputting these from the operational suite after LFRic goes operational.

The existing UM calculations can be found in:
[src/atmosphere/convection/diagnostics_conv.F90](https://github.com/MetOffice/um/blob/main/src/atmosphere/convection/diagnostics_conv.F90)
and the ICAO height calculation in:
[src/atmosphere/physics_diagnostics/icao_ht.F90](https://github.com/MetOffice/um/blob/main/src/atmosphere/physics_diagnostics/icao_ht.F90).

The pressure at the model rho-level corresponding to the conv cloud base or top height is taken; this is then converted to a height based on the ICAO standard height / pressure profile.

### Further details of the issue.

_No response_