Merge branch 'ci-template-kaniko-flexible' into 'master'

Update the Kaniko template to make the job be extendible

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/144352



Merged-by: Furkan Ayhan <furkanayhn@gmail.com>
Approved-by: Michael Friedrich <mfriedrich@gitlab.com>
Approved-by: Furkan Ayhan <furkanayhn@gmail.com>
Co-authored-by: Kjetil Torgrim Homme <kjetil.homme@redpill-linpro.com>