Schedule weekly VM image builds in Terraform (#2982)

- Run Create Linux VM image (Mon 04:00 UTC) and Create Windows VM image
(Mon 05:00 UTC, staggered 1h so testing presubmits do not collide with
bk-testing-docker recreation) outside Munich and New York working hours

- Codify the existing every-10-minute Collect Infra CI-Metrics schedule.