chore: update ci label reqs and changelog generation

[macintoshpie]

Any background context you want to provide?

BSync is starting to use PRs for tracking changes to the schema instead of issues.

What does this PR do?

• Changelog now uses PRs to determine breaking/non-breaking changes to schema as well as categories affected
• Require PRs to have one of the labels "Non-schema Change" if it doesn't affect the schema
• Requires PRs affecting the schema to include a scope label (e.g. "Schema: Systems")

How should this be manually tested?

• Run the changelog script, things should work as expected

What are the relevant tickets?

Screenshots (if appropriate)

New changelog format