ESC: GCloud OIDC docs should show comprehensive outputs (env var and Pulumi config)

[jkodroff]

https://www.pulumi.com/docs/esc/integrations/dynamic-login-credentials/gcp-login/

We don't show how to output the values. GCloud is particularly tricky to get OIDC to work for all use cases (Pulumi + the gcloud CLI).

We have that "documented" in this code sample, but it should also be in the docs so that no one has to trip over it like I did:

https://github.com/pulumi/examples/blob/master/gcp-ts-oidc-provider-pulumi-cloud/index.ts#L85-L108