Add packages tagged table to release management toil dashboard

For issue: gitlab-com/gl-infra/delivery#2819 (closed)

Adds a user-friendly visualization of number of packages tagged (delivery_packages_tagging_total) by release type to the Release Management Toil dashboard

Interacts with the time range ($__range variable)

24 hours expiration demo link: https://dashboards.gitlab.net/dashboard/snapshot/Jh2ZS3Y2yBPwpL77c2gux7pIWYUb2f4i

You can generate the link again by running:

$ ./test-dashboard.sh delivery/release_management_toil.jsonnet
Installed https://dashboards.gitlab.net/dashboard/snapshot/Jh2ZS3Y2yBPwpL77c2gux7pIWYUb2f4i - delivery: Release Management Toil