fix: Requests Respect config.projectIdRequired === false

[danielbankhead]

Fixes #711 🦕

Important: Will need to port fix to https://github.com/googleapis/nodejs-storage/

[danielbankhead]

Checking for the projectId as a fallback when it is not available to preserve existing behavior. Currently, consumers may not expect projectIdRequired to affect things at the request level - this is here to ensure backwards compatibility. Cases:

• this block is not called (skips catch block): API is fully projectId-free.
• this is called (is caught): since the projectId was not checked before, this preserves that call. Net = 0 new calls are made

[danielbankhead]

Expanded this block for readability.

[ddelgrosso1]

Overall I think the code changes look good. However, what is the plan for testing this as to not potentially impact consumers in case this causes unforeseen issues?

[danielbankhead]

@ddelgrosso1 I think this is overall safe - here's an overview:

• if projectIdRequired !== false, the codepaths are the same as before
• if projectIdRequired === false it will attempt to use the default project id placeholder (which throws if a project id is required), and will fallback to checking for a project id (preserving existing behavior)

Additionally, all API calls are in the same order as before

[bcoe]

Awesome thanks for upstreaming this work @danielbankhead 👏

Will defer to @ddelgrosso1 for review.