chore: replace stale bot with GH actions workflow

[mowies]

This PR

• replaces the probot/stale GH app with a GH actions workflow
• this was done because probot/stale is no longer maintained and deprecated since Officially deprecate app and repository probot/stale#430

[netlify]

✅ Deploy Preview for keptn-lifecycle-toolkit ready!

Name	Link
🔨 Latest commit	6d4ced2
🔍 Latest deploy log	https://app.netlify.com/sites/keptn-lifecycle-toolkit/deploys/649ae0aef88d44000749d4da
😎 Deploy Preview	https://deploy-preview-1629--keptn-lifecycle-toolkit.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[odubajDT]

Can you please fix the yamllint check ? :)

[codecov]

Codecov Report

Merging #1629 (2179c05) into main (7087bb6) will decrease coverage by 5.87%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1629      +/-   ##
==========================================
- Coverage   63.37%   57.50%   -5.87%     
==========================================
  Files         142      108      -34     
  Lines       10822     9231    -1591     
==========================================
- Hits         6858     5308    -1550     
- Misses       3708     3729      +21     
+ Partials      256      194      -62     

see 62 files with indirect coverage changes

Flag	Coverage Δ
certificate-operator	68.55% <ø> (ø)
component-tests	59.09% <ø> (-1.22%)	⬇️
lifecycle-operator	?
metrics-operator	?

Flags with carried forward coverage won't be shown. Click here to find out more.

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
No Duplication information

[mowies]

@odubajDT done :)