Consolidate auto-insertion pipelines

There's a significant amount of "sprawl" across our insertion pipelines--one for each release branch, one for PR validation, one for master validation, etc.

It would be great if we could consolidate all the pipelines that create draft insertions, for example. The insertion tool should be able to handle the variations between e.g. official builds for QB branches and validation builds by just looking at the tags on the build.

Ideally we could have a pipeline that creates draft/validation insertions and another pipeline that creates auto-merging insertions.

Start by mapping the existing insertion pipelines and how draft, validation, official-build, and auto-merging variations are selected from build tags. Done means the current pipeline sprawl is consolidated into one pipeline for draft/validation insertions and another for auto-merging insertions, while preserving the stated build variations.

Written by the indexing model from the issue text.