Move variants/compiler flags from `spack.yaml` to relevant `package.py`s

[CodeGat]

See https://github.com/ACCESS-NRI/ACCESS-OM3/pull/5#issuecomment-2089614861 and spack.yaml in https://github.com/ACCESS-NRI/ACCESS-OM3/pull/5/files#diff-e8582e74fa156f4e5729a850e52b24f2fde2d815c2c9c360f88c4cf90db851ab

In this PR:

• Propagate build_type==RelWithDebInfo down the relevant dependencies in access-om3-nuopc
• Move compiler flags into the depends_on functions (if they are intel compilers)
• Removed +deprecated_io variant
• Removed +install_libraries, instead using the default ~install_libraries

Closes #102

[CodeGat]

~Athough installing is having a problem with fmss +large_file variant...~ Might be an issue with the dev image I'm using

[CodeGat]

Very good to know that depends_on is composed like that. Thanks - ready for re-review.

[CodeGat]

Thanks for going through it with me! It'll make future package.py changes a bit less Changes Requested, I'm sure.