Include PR info into release version

[artem-zinnatullin]

Apparently, any PR to this repo whether made by untrusted 3rd-party or by a member of Buildkite team which successfully ran CI publishes:

• Helm charts
• Docker Image of Controller

They get versioned via git describe like so:

Where g59acf83 in ghcr.io/buildkite/agent-stack-k8s/controller:0.15.0-5-g59acf83 indicates a short commit sha.

The security issue here is that for a typical end user who wants to grab what they think is latest build they just go to the packages linked right on GitHub and grab a latest build like the controller:0.15.0-5-g59acf83

But in reality controller:0.15.0-5-g59acf83 is build from an unmerged PR #381!

In worst case scenario such PRs can be made by a malicious 3rd-party doing god knows what like leaking user credentials or doing Remote Code Execution in their CI setup, PRs are not yet merged onto main branch of original repo but already appear in the available packages list: here is controller build from my old PR as I found out now https://github.com/buildkite/agent-stack-k8s/pkgs/container/agent-stack-k8s%2Fcontroller/218244275?tag=0.11.0-1-g43e4777

As of right now if I understand correctly a member of Buildkite team needs to manually approve CI to run on a 3rd-party PR, which should prevent malicious code from being published, but for the end user nothing indicates the difference between the releases on the package page.

This PR adds PR information into the release version name so it's clear that you're not taking some latest main branch commit release: controller:0.15.0-5-g59acf83 → controller:0.15.0-5-g59acf83-PR-381

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I do want to emphasize that having 3rd-party PRs release as packages is actually very useful for testing the changes by the community and I'd love Buildkite to keep that feature, but to do so in a secure manner the release names need to clearly indicate that it is an untrusted 3rd-party PR release.

[DrJosh9000]

This is a problem I'd definitely like to solve, and this is a reasonable approach.

Another approach we came up in discussion was: publish the "edge" and "PR" builds to a subfolder (e.g. agent-stack-k8s/pkgs/controller/edge), with only the numbered releases at the main path.