BANDA-899 chore: add GitHub Actions workflow to deploy Workers

[jahands]

Changes:

• moved some of the setup (install pnpm/node/dependencies) to a shared composite action
• renamed test-and-check.yml to branches.yml - it no longer runs on the main branch
• added a new main.yml workflow for running checks on the main branch and then deploying to staging
• added a new release.yml workflow for opening pull requests based on changesets
  • as part of this, I added a new cli to packages/tools: runx - this is used for deploying the newly published Workers after Version Packages PRs are merged.
  • the cool thing about this is that it will only deploy Workers who's version changed in the Version Packages PR