[FEATURE] When running workflows on behalf of my end users, I want to use accounts that were connected with Pipedream OAuth

Right now, when executing workflows on behalf of my end users with Pipedream Connect, [I can only use connected accounts that are using my own custom OAuth client](https://pipedream.com/docs/connect/oauth-clients#using-pipedream-oauth), but I'd rather use Pipedream's.