Migrate sync job to GitHub Actions and remove CircleCI config

[ankatiyar]

Description

Fix #2968
Also fix #3318

Development notes

sync.yml

The first part of the workflow is to merge the commits to develop if they can be merged cleanly otherwise open a PR.
This workflow uses the same script that we did with CircleCI except it's triggered by GHA instead. This workflow runs on a schedule (every 30 mins) but can also be dispatched manually.

🔔 Workflow in action on my fork - https://github.com/ankatiyar/kedro/actions/workflows/sync.yml

.github/workflows/label-pr.yml & .github/labeler.yml

This second workflow uses the labeler action. The workflow is in .github/workflows/label-pr.yml and the configuration is in .github/labeler.yml. This workflow labels any PRs on the branch merge-main-to-develop with the "automerge" label which is required by the auto-merge action described below.
NOTE - this action can be extended in the future for auto labelling of other PRs such as "Community" etc

auto-merge-prs.yml

This action is the final part of the workflow - it merges any PRs labelled "automerge" with a merge commit. It uses the auto-merge action. This is also a scheduled action (every 60 mins) and can also be triggered manually.

🔔 ankatiyar#14 - PR created, labelled and merged with the above workflows on my fork

Removal of all CircleCI stuff

Since it was the only workflow left and wouldn't make sense to let it run on both platforms incase there are conflicts with merging.

NOTE - I wasn't able to get the second script we run used to run with CircleCI tools/circleci/github_scripts/attempt-merge-pr.sh so this is an alternative solution for the merging of PRs with marketplace actions.

Developer Certificate of Origin

We need all contributions to comply with the Developer Certificate of Origin (DCO). All commits must be signed off by including a Signed-off-by line in the commit message. See our wiki for guidance.

If your PR is blocked due to unsigned commits, then you must follow the instructions under "Rebase the branch" on the GitHub Checks page for your PR. This will retroactively add the sign-off to all unsigned commits and allow the DCO check to pass.

Checklist

• Read the contributing guidelines
• Signed off each commit with a Developer Certificate of Origin (DCO)
• Opened this PR as a 'Draft Pull Request' if it is work-in-progress
• Updated the documentation to reflect the code changes
• Added a description of this change in the RELEASE.md file
• Added tests to cover my changes
• Checked if this change will affect Kedro-Viz, and if so, communicated that with the Viz team

[merelcht]

This looks really good! Great job @ankatiyar ⭐ 👍 I am in favour of using the GH actions marketplace where we can. The only question I have is whether it's possible to add a slightly longer description in the workflow .yml files to explain what they do? Otherwise I think it would be a good idea to document in our wiki what each of these jobs do.

[SajidAlamQB]

Awesome work @ankatiyar! 🌟 The two new GH actions make sense and look to be working well. Excited to see this in action!

[SajidAlamQB]

No more CircleCI! 🥳

[ankatiyar]

@merelcht I've added comments to the workflows but I'll also create a wiki for the CI setup in general.