Renovate already detects PRs mistakenly closed during a certain time period when a bug was present. Now, it will rename those so that they are no longer detected and the ignore code does not have to remain indefinitely.
This feature adds a new behaviour to Renovate, where it will now add a comment to any existing closed PRs that are "blocking" currently valid updates. A new API function "ensureComment" has been added, its purpose is so we can ensure there exists only one comment with a certain subject/heading. This lets us prevent duplicates as well as update existing, without having to keep state about it. ensureComment needs porting to gitlab, but should be quite easy.
This is a major refactor of branch code to prepare for Yarn workspaces plus creating PRs for branches with failing lockfiles. Marked as "feature" to cause a minor version bump due to the moderate chance of accidentally breaking something.
