Add back jq to spack buildcache push

[CodeGat]

See failed run: https://github.com/ACCESS-NRI/build-ci/actions/runs/9608705872/job/26501970133#step:4:8470

Using spack buildcache push without a list of specs assumes that you want to push all of them. However, if not all of them are installed (as is the case in our dependency image, which spack install --only dependencies ...) it fails. So leaving the jq in was needed.
To solve the original issue in #168, we now get both the name of the package, and the hash, so we can push up different versions of the same package.
We also remove the --allow-root flag as it is assumed in 0.21, and removed in 0.22.

In this PR:

• setup-spack-envs.sh: Removed --allow-root (assumed in 0.21), added back hash-delineated jq

[jo-basevi]

LGTM