* ci: darwin stacks: update tags following system updates
* disable SPACK_CI_DISABLE_STACKS; only enable *darwin* stacks for testing
* manually chmod u+w tmp/ before cleanup due to issue#49147
* comment out failing specs for now
* re-enable logic for disabling stacks
* add explanatory comment for darwin after_script additions
* remove more darwin-only targetting
* restore build_stage to default location
* move build-job-remove out of individual darwin stacks into darwin top level config
* keep build_stage in $spack/tmp for now
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