feat: add universe domain support to core, bigquery, storage, and pubsub

[bshaffer]

Add support for Universe Domain to BigQuery and Storage via modifications to RequestWrapper, RequestWrapperTrait, and RestTrait. Add support in PubSub via GrpcTrait.

Still needs:

• verify behavior for when API Keys and Access Tokens supplied outside the GDU
  • Translate is the only Client that accepts a "key" argument for API Keys, but shouldSignRequest can bypass credential check
  • Both raw access tokens and API keys are allowed to bypass the check.
  • shouldSignRequest bypasses the check (and the sending of credentials)
  • In our implementation, we will not allow raw access tokens. API keys are allowed.
• design approval (@vishwarajanand)
• unit tests
• manual tests in universe domain testing environment

[vishwarajanand]

I observed that ApplicationDefaultCredentials::fetchAuthToken() produces an array with just 1 key, access_token while using a universe domain, while in GDU, it produces an array with keys access_token, expires_in (comes from oAuth2 and almost always has value 3599), token_type (value is Bearer).

Upon discussion with @bshaffer, it seems that TPC uses jwt, so if I call $credentials->useJwtAccessWithScope(); in GDU, I get an array with just access_token key. I think we need to change this behavior here.

We can change it to something like:

        return [
            'access_token' => $access_token,
            'expires_in' => $this->auth->getExpiry(),
            'token_type' => 'Bearer',
        ];

[bshaffer]

I observed that ApplicationDefaultCredentials::fetchAuthToken() produces an array with just 1 key, access_token

To be fair, this is a behavioral difference between SSJs and the oauth token endpoint, and is not related to the Universe Domain support (although it did help us uncover the discrepancy)

[vishwarajanand]

Is my environment broken or is this an actual issue with the token?
https://paste.googleplex.com/5467801802768384
I am seeing an access_token in RequestWrapper but when its used in BQ or Storage client, I am seeing errors as mentioned in the log. This seems to be consistent with REST calls too so looks like not a library issue.

[bshaffer]

Is my environment broken or is this an actual issue with the token?

You are using the GDU endpoint (bigquery.googleapis.com) instead of the URL for the Universe Domain you've provided (bigquery.apis-tpclp.goog), so the exception you're seeing is expected.

[vishwarajanand]

There are some merge conflicts, otherwise LGTM