Labels with associated milestone

What

Labels which are tied to a milestone, with their name either being prefixed by it (10.6: Regression), or parametrized (Regression introduced in #{milestone}).

Using labels lets us filter effectively and adding a milestone lets us tie that label to a specific release.

Why

Some times we want to add searchable information to an issue or merge request which is directly tied to a milestone.

We want to be able to filter by that information as well as looking at statistics to identify trends.

Milestone can become overloaded with multiple meanings: the milestone where a regression was introduced, the milestone a feature is intended to start work in, the milestone a feature is expected to be completed by, the release a bugfix merge request should be cherry picked into, etc. Sometimes we also want multiple milestones for a label: e.g. Cherry-Pick into 10.6 and also Cherry-Pick into 10.5.

Why not

This might be overcomplicated, and creating labels for each milestone could be an effective workaround.

Related ideas

@joshlambert proposed a "Found In" milestone feature in the 10.6 retrospective. Might be worth creating a separate issue for as that is a simpler idea