[CT-3491] Secret-Handling Review

### Housekeeping

- [X] I am a maintainer of dbt-core

### Short description

Review the dbt-core source code, considering all the ways dbt explicitly supports secrets as inputs, and inspect the code which handles the secrets in order to ensure that adequate safeguards are in place to prevent the secrets from leaking unintentionally into logs, error messages, output artifacts, or requests to external services other than those intended.

### Acceptance criteria

Report on the inspection that was performed, describing any issues found and/or follow-up recommended.

### Impact to Other Teams

None.

### Will backports be required?

Only if serious issues are found.

### Context

_No response_