Add support to only return failed states to slack. #46840
What does this PR do?
Add support to only return failed states to slack via slack_retuner.
What issues does this PR fix or reference?
Now, you can still use
Commits signed with GPG?
@mwerickso There is a lint error on this change here: https://jenkins.saltstack.com/job/PR/job/salt-pr-lint-n/20708/violations/file/salt/returners/slack_returner.py/
Can you fix that up?