`go-kit/kit/log` was deprecated and generating warnings
# Checklist for submitter
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<!-- Note that API documentation changes are now addressed by the
product design team. -->
- [x] Manual QA for all new/changed functionality
Add a config setting to allow copying message fields and decorations into Google Pub/Sub attributes, making it possible to use these values for subscription filters.
Adds Google Cloud PubSub logging for status and results.
This also changes the Write interface for logging modules to add a context.Context (only used by pubsub currently).
