Move NEPTUNE Python dependencies into its their own package neptune-python-env, remove legacy environment variables for NEPTUNE

[climbfuji]

Summary

This PR moves the full NEPTUNE Python dependencies into their own package neptune-python-dev. Only the basic dependencies on f90nml and python-dateutil remain in neptune-env (needed by NUOPC).

The espc variant is turned off by default in neptune-env, but the neptune-dev template enables it. Likewise, the xnrl variant is turned off by default in neptune-python-env, but the neptune-dev template enables it.

Several legacy environment variables for hdf5, libyaml, p4est are removed from configs/common/modules_*.yaml.

Testing

• Manual testing on @climbfuji's development system blackpearl with gcc in neptune_atmos
• CI testing in NEPTUNE on Nautilus with Intel classic, Intel llvm, GNU
• Manual testing on @climbfuji's development system blackpearl with gcc in dsapi
• Manual testing on @climbfuji's development system blackpearl with gcc in ioapi
• spack-stack CI (see below)

Applications affected

NEPTUNE, JEDI-NEPTUNE

Systems affected

None

Dependencies

n/a

Issue(s) addressed

Working towards #1342 (for NEPTUNE only)

Checklist

• This PR addresses one issue/problem/enhancement, or has a very good reason for not doing so.
• These changes have been tested on the affected systems and applications.
• All dependency PRs/issues have been resolved and this PR can be merged.