Merge topic 'ci-pwsh-cleanup'

94b27ccc36 ci: add support for gitlab-runner 'shell = pwsh' executor
de32c8ddbe ci: start every windows job with custom environment script
906b1a0bc4 ci: allow powershell variables assigned in env scripts to persist

Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: Ben Boeckel <ben.boeckel@kitware.com>
Merge-request: !7667