Add MR pipeline

Why is this change being made

Currently, the pipeline only runs on schedule. This makes it hard to obtain builds for changes.

This change results in three jobs in the release stage which run conditionally and publish the same database with different tags:

Job	When	Example
release commit	MR commits	trivy-db-glad:d7d1bce9d73d1bcf65d4aae9fe93d51370a03b33
release date	only on schedule	trivy-db-glad:2022041317
release latest	only on schedule for main branch	trivy-db-glad:2