Add GCP copyright check

[damemi]

The .licenserc.json and license check just look for OpenTelemetry copyright. We're currently adding GCP files to the ignore section of licenserc and manually checking for copyright notices during review. We should update the CI check to tell it which files should have GCP copyright, which ones should have otel copyright, and possibly some that have both

[aabmass]

Discussed in triage, one other option is to move over the GCP license checker bot https://github.com/googleapis/repo-automation-bots/tree/main/packages/header-checker-lint which we use in our other repos.