Add timing and thread info to sources.json artifact

[drewbanin]

resolves #3804

Description

This PR adds the following fields to the sources.json artifact:

• timing (same format as run_results.json)
• execution_time
• thread_id

Big question here is: is this the right change to make, or should we pursue moving this information into the run_results.json file instead? I think that adding it to sources.json is a net-positive, it isn't a breaking change, and it doesn't preclude us from migrating this metadata into the run_results.json file in the future.... so why not? :)

Small question: if we did want to merge this, where should it live in the changelog?

Checklist

• I have signed the CLA
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• I have updated the CHANGELOG.md and added information about my change to the "dbt next" section.

[jtcohen6]

I can respond to the substantive point over in #3804 (comment). In the meantime, this feels like an uncontroversial improvement. Happy to get it in & under the wire for v0.21.0! We'll just want to bump the schema version for sources.json in v0.21.

Logistically speaking, you can just merge to develop once the tests pass. We're planning to merge develop into 0.21.latest ahead of cutting v0.21.0-rc1.

[drewbanin]

Right on! I just updated the changelog and put this in for 0.21.0 and will merge when all is green :)