Consider automating package publishing on every PR

[petertonysmith94]

Summary

After migrating our package publishing for next and PR from NPM to GitHub packages in #3639, we could consider automatically publishing every PR to GitHub packages.

This will also enable us to:

• Run associated integration tests on every PR
• Remove the manual pr-release workflow.

Follow ups

• We could consider an automated job to remove these published packages from GitHub packages (this could be via a CRON job).

[arboleya]

A cleanup action to purge what's been merged is still valid, but because we're open-source, it seems we don't necessarily pay for storage for GitHub packages. This means that the cleanup routine can be a follow-up issue.

[arboleya]

We can also have a simple workflow/test that assets something by installing the tag from scratch (after publishing) instead of referencing it from the workspace (before publishing). This is to ensure that the published tag can be installed/used.

With the above, I believe we don't need:

• Add test helpers for testing PRs without having to release them #3547