Add generate_wombatlite_ic.py script

[dougiesquire]

This PR adds a simple script for generating the ACCESS-OM3 WOMBATlite initial conditions for those tracers that are initalised to constants (a la ACCESS-OM2).

[anton-seaice]

I think if this had an example use it would be clearer what grid file was needed etc .

In /g/data/vk83/configurations/inputs/access-om3/wombat/initial_conditions/global.1deg/2024.04.02/init_ocean_wombatlite.res.nc, there is a time dimension. Is that needed ?

It looks like this needs ocean initial conditions as a template? If that is true, that should be clearer in the description

Also, cchecker.py shows many things but maybe these are worth setting:

variable "caco3" missing the following attributes:
* coverage_content_type
* standard_name

variable "caco3_sediment" missing the following attributes:
* coverage_content_type
* standard_name

variable "det" missing the following attributes:
* coverage_content_type
* standard_name

variable "det_sediment" missing the following attributes:
* coverage_content_type
* standard_name

variable "phy" missing the following attributes:
* coverage_content_type
* standard_name

variable "time" missing the following attributes:
* standard_name

variable "zoo" missing the following attributes:
* coverage_content_type
* standard_name
*```

[dougiesquire]

Also, cchecker.py shows many things but maybe these are worth setting:

variable "caco3" missing the following attributes:
* coverage_content_type
* standard_name

What is coverage_content_type? I don't think many of these variables have valid CF standard names.

[anton-seaice]

Looks good :)