Added Azure.ACR.SoftDelete rule

[BenjaminEngeset]

PR Summary

Added Azure.ACR.SoftDelete rule.

Azure Container Registries should have soft delete policy enabled.

Fixes #1674

PR Checklist

• [x] PR has a meaningful title
• [x] Summarized changes
• [x] Change is not breaking
• [x] This PR is ready to merge and is not Work in Progress
• Rule changes
  • [x] Unit tests created/ updated
  • [x] Rule documentation created/ updated
  • [x] Link to a filed issue
  • [x] Change log has been updated with change under unreleased section
• Other code changes
  • [ ] Unit tests created/ updated
  • [ ] Link to a filed issue
  • [ ] Change log has been updated with change under unreleased section

[BenjaminEngeset]

@BernieWhite

Ready for PR.

Notes from my side

• The rule will only run when geo-replication and retention policy are not configured. This is preview limitation. This has both advantages and disadvantages, but preview limitations are what they are currently. So the rule will be skipped for some of our customers.
• The rule will require refactoring once the limitations are gone, so we have to watch out for that and adjust accordingly.

[BenjaminEngeset]

@bengeset96 Great work! Just a few minor tweaks otherwise all good.

@BernieWhite

Done. I think we are ready.