fix(js/plugins/google-cloud): pass projectId through to GoogleAuth client

[MichaelDoyle]

WIP - testing in progress

I saw a bug in Discord where projectId being set in the options was not respected; in the end an alternative solution was found. After working on refactoring the docs, I realized we are not appropriately passing projectId along to the GoogleAuth client.

The specific use case is as follows: If the developer provides an external credential (either via credentials option, or via env variable) they must also provide the target projectId to the client.

In all other cases, projectId should be available and inferred from the client, as it will not work without the projectId set.

One possible point of confusion seems to arise with local user auth in development (i.e. gcloud auth application-default login). In this case, projectId might not be set. The solution is to provide it during auth (--project), set the gcloud cli default project, or set the environment variable GCLOUD_PROJECT.

Checklist (if applicable):

• PR title is following https://www.conventionalcommits.org/en/v1.0.0/
• Tested (manually, unit tested, etc.)
• [N/A] Docs updated (updated docs or a docs bug required)