Enable netCDF compression

# ✨ Feature Request
ANTS default behaviour is to save netCDFs without compression.

Given netCDFs are typically saved in ANTS as part of a workflow to either produce an ancillary or to produce a source file for UG-ANTS, and we can load compressed netCDFs, we should make the option to save with compression available to end users. Lossless compression is already available via the iris save interface.

This should be for the standard netCDF save only, not the UKCA save interface (unless there is confirmation that the UM can load compressed UKCA netCDF files).

## Context
When this is implemented, we should consider a future issue for making compression the default.

Start by tracing ANTS's standard netCDF save path and the Iris save interface it uses; keep the UKCA save interface separate unless compatibility is confirmed. Done means end users can opt into lossless compression for standard netCDF saves without changing the default behavior.

Written by the indexing model from the issue text.