Fixes after asdf to mise migration

fix: pass -S to env to split arguments

fix: move the asdf to mise migration script

So it does not get copied into the repositories

These were brought up in !196 (comment 2036318039), these have been tested out by running:

copier update --trust --skip-answered -r bvl/mise-fixes

Which resulted in https://gitlab.com/gitlab-com/gl-infra/capacity-planning-trackers/gitlab-dedicated-staging/-/merge_requests/54