[Feature] Summary stats for source freshness run

Is this your first time submitting a feature request?

[X] I have read the expectations for open source contributors
[X] I have searched the existing issues, and I could not find an existing issue for this feature
[X] I am requesting a straightforward extension of existing dbt functionality, rather than a Big Idea better suited to a discussion

Describe the feature

Print summary stats for a "dbt source freshness" run (how many passed/warn/error), similar to summary stats for a "dbt test" run

Describe alternatives you've considered

Users of dbt write individual custom scripts to parse the output of source freshness to find and alter failed checks, this would be easier with a summary stats line at the end.

Who will this benefit?

All users of dbt who are using source freshness runs to monitor production (or other environment) data availability in a manual or automated fashion.

Are you interested in contributing this feature?

No response

Anything else?