refactor(resource-detector-gcp): migrate away from getEnv()#2705

pichlermarc merged 2 commits intoopen-telemetry:mainopen-telemetry/opentelemetry-js-contrib:mainfrom

dynatrace-oss-contrib:chore/gcp-stop-using-getenvdynatrace-oss-contrib/opentelemetry-js-contrib:chore/gcp-stop-using-getenvCopy head branch name to clipboard