[IDE jobs] only post interesting notifications to Slack

[filiptronicek]

Description

This PR changes all IDE jobs which have previously posted a message to Slack every time they were run to now only post when they are interesting to us.
This includes them failing or being fixed (going from failing to passing).

This is all achieved by this little snippet:

- name: Get previous job's status
  id: lastrun
  uses: filiptronicek/get-last-job-status@main
  with:
    workflow-id: 18268462
- name: Slack Notification
  if: always()
  if: ${{ (success() && steps.lastrun.outputs.status == 'failed') || failure() }}
  ...

Progress

• https://github.com/gitpod-io/gitpod/blob/main/.github/workflows/code-nightly.yaml
• https://github.com/gitpod-io/gitpod/blob/main/.github/workflows/jetbrains-auto-update-template.yml
• https://github.com/gitpod-io/gitpod/blob/main/.github/workflows/jetbrains-update-plugin-platform-template.yml
• https://github.com/gitpod-io/gitpod/blob/main/.github/workflows/jetbrains-updates-template.yml

Related Issue(s)

Fixes #11771

How to test

For the workflows that have manual triggers (can be run by a Run Workflow button on the Actions page), you can just trigger it and wait for it to finish. If it succeeds then it should not output anything to the Slack channel and the Action step should be skipped.

Release Notes

NONE

Werft options:

• /werft with-preview

[andreafalzetti]

LGTM! 👏