Regional configs to read input data using new XIOS API for time varying fields

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

Yes. PR for implementing this functionality is #735

### Brief description

Currently the IO API to XIOS that the regional configurations use to read in data fields (e.g. time varying ancillaries, etc.) in specified time chunks (using the `time_axis_type`), which is a more clunky that the newer API which allows for time-varying fields.

### Further details of the issue.

The purpose is the migration of GungHo time-varying ancillaries from the legacy `time_axis_type` path to the newer file-owned temporal path in `lfric_xios_file_type`.

The old ancillary path in `science/gungho/source/driver/init_ancils_mod.f90` creates one `time_axis_type` per ancillary group, attaches raw time-window fields to that axis, inserts the axis into `model_axes%ancil_times_list`, and relies on the driver to refresh the fields.

The goal is to move temporal cache ownership out of the driver and into the file object, while keeping reads bounded to the time slices actually needed by the run.