Stac 12220 - make state location configurable from check config

[zandrewitte]

Step 1: Link to Jira issue
https://stackstate.atlassian.net/browse/STAC-12220

Step 2: Description of changes

Make the check state location configurable in the conf.d of the check.
Make Check State and Auto Snapshotting Agent Check mixins.

Step 3: Did you add / update tests for your changes in the right area?

• Unit/Component test
• Integration test

Step 4: I'm confident that everything is properly tested:

I got a PO / QA Approval by:

• Name

Step 5: Can we ship this feature to production?

• Yes, I'm proud of my work. Ship it! 🚢