[CT-2820] Configure Tests for Datadog Visibility

[emmyoop]

Get the following repos set up in Datadog to start accepting data
Generate and store DD API key in all repos
Update tests to send data to DD

• dbt-core - add env vars for datadog ci visibility #8097
• dbt-snowflake - add datadog env vars dbt-snowflake#690
• dbt-redshift - add datadog env vars dbt-redshift#539
• dbt-bigquery - add datadog env vars dbt-bigquery#829
• dbt-spark - add datadog env vars dbt-spark#836 backout out for now - questions on CircleCI

These all need to be backported to ensure the data gets sent for release branches as well.

• dbt-core - backported
• dbt-snowflake - backported
• dbt-redshift - backported
• dbt-bigquery - backported
• dbt-spark - backported

Acceptance Criteria

Test data is populated in Datadog

Reference:

Datadog Python docs
coud-ui PR

[emmyoop]

We won't be hooking up dbt-spark until it moves CI into GitHub Action