Google Cloud Build support

[mitchell-codecov]

Is your feature request related to a problem? Please describe.
Google Cloud Build is not implemented as a CI provider.

Describe the solution you'd like
Google Cloud Build should be implemented as a CI provider (e.g., "provider_googlecloudbuild.ts").

Additional context
#823 (comment)

[escarls]

I have a PR for codecov_cli that adds Google Cloud Build CI support.
I am understanding that codecov_cli is the way forward.
If I'm wrong on that, I'd be happy to try to port the functionality here also.

[drazisil-codecov]

CLI is indeed the preferred tool. For several reasons, some customers are still using the uploader, but it is my understanding that we aren't adding additional features here. Thanks for checking.

[drazisil-codecov]

@rohan-at-sentry Can we close this issue in favor of the CLI?