Update dbt Docs with improvements to Metric documentation

[drewbanin]

Description

This PR adds a new build of the dbt-docs index.html file via dbt-labs/dbt-docs#285. Specifically, it includes improvements to how metrics are referenced in the Docs UX and DAG viz. It:

• Draws DAG edges for expression metrics (ie. a metric that depends on one or more other metrics)
• Renders labels, types (expression vs. aggregate), and SQL for each metric
• Uses the metric label rather than the name in the sidebar + DAG viz + search results
• Supports search results on metric + label name (eg. both "arpc" and "Revenue") should pull up the arpc metric

Checklist

• I have read the contributing guide and understand what's expected of me
• 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 opened an issue to add/update docs, or docs changes are not required/relevant for this PR
• I have run changie new to create a changelog entry

[github-actions]

Thank you for your pull request! We could not find a changelog entry for this change. For details on how to document a change, see the contributing guide.

[drewbanin]

oops - closing in favor of #5255