Feature: Make workflow instructions depend on their triggering webhook events

[yardasol]

Background and motivation

Right now, our release workflow assume we are only working on one release at a time. If we ever need to backport a bugfix, our workflows won't work.

Description of idea

We should make our workflows specific to the webhook event that triggers them

Implementation details

We'll need to use github.event context to get this information, so we can run multiple versions of populate-releasenote.yml, next-release-minor.yml,etc, for each release that gets the bugfix.

Useful resources:
- Webhook object for releases

• github.event context

Potential snags

This is coupled to #116 and #129.