Use compiled_sql from manifest (no injected_sql, no run_results)

[jtcohen6]

resolves #146

Tested with dbt-labs/dbt-core#2834. Both ephemeral models and models that select from ephemeral models are looking good.

TODO before merge

• We need to rebase dev/kiyoshi-kuromiya onto v0.18.1 to grab all the code around exposures. Then I'll need to regenerate the data/ artifacts.

Checklist

• I have signed the CLA
• I have generated docs locally, and this change appears to resolve the stated issue
• I have updated the CHANGELOG.md and added information about my change to the "dbt next" section.

[drewbanin]

This is awesome! Glad we can drop the dep on the run_results.json file... pretty funny we had been using it all this time :)

Approved on my end. Nice work @jtcohen6!