[FEATURE] Mandatory labeling for PRs

[Swiddis]

Is your feature request related to a problem?
Most OpenSearch repositories, including this one, have an action that automatically drafts release notes as PRs are merged. Since we typically don't label our PRs, this feature isn't seeing usage, and slowing down release note processes.

What solution would you like?
In the name of not relying on everyone to start automatically, I propose introducing a CI check that mandates labeling PRs. This is already used in the observability repo and by & large makes the generation process easier.

What alternatives have you considered?
The main alternative is manually applying them without any strict checks, which could theoretically work (and would more flexibly allow deliberately ignoring inconsequential PRs in release notes), but doesn't seem to be applied.

Do you have any additional context?
Read about release-drafter, Ashwin's Proposal for automating release notes based on labels, or the WIP PoC for release note generation in OSD.