Add a deprecation warning for timeNanos.
Add a deprecation warning for timeNanos.

laramiel/fluent-plugin-google-cloud,a-robinson/fluent-plugin-google-cloud,arthurdarcet/fluent-plugin-google-cloud,brint/fluent-plugin-google-cloud,GoogleCloudPlatform/fluent-plugin-google-cloud,mururu/fluent-plugin-google-cloud,swalkowski/fluent-plugin-google-cloud,cosmo0920/fluent-plugin-google-cloud,senthilkumar-kj/fluent-plugin-google-cloud