multiple reads of time information from ancillaries

is appears that time information is required by `lfric_atm` ranks in order to configure the XIOS context

this information is read from files directly by `lfric_core` netCDF code prior to the XIOS context being defined

e.g.
* `qrclim.sstice_sst.nc`

however:
1. files are opened using `nc_open` rank by rank
* this scale very badly for parallel storage systems
2. two different places in the code open the file to obtain similar information, but don't communicate with eachother.
a. [get_netcdf_time_dim](https://github.com/MetOffice/lfric_apps/blob/main/science/gungho/source/physics/time_dimensions_mod.F90#L69)
b. [open_file](https://github.com/mo-marqh/lfric_core/blob/main/infrastructure/source/io/lfric_ncdf_file_mod.F90#L121)

Tasks:
1. reduce the requirement to open individual files for `lfric_atm` to one call, not two!
2. ensure that many ranks do not issue many `open` calls:
a. by using `nc_open_par` && collective reads
b. by using a `rank0` read and `MPI` distribute pattern

(consider implementing and evaluating both patterns prior to full adoption of one)