Cloud Logging in processor does not show severity

[KyleJu]

After the previous migration from AppEngine logging to Google Cloud Logging, Cloud Logging in processor needs improvements:

• Logs in the processor are not labelled with proper severity, thus very difficult to spot and filter error logs
• Logs are not structured, thus difficult to find related logs
• Filled with unimportant log entries ,e.g. server health checks

[gsnedders]

On the results-processor side we have:

wpt.fyi/results-processor/main.py

Lines 27 to 30 in d6339c4

	# Hack to work around the bad logging setup of google.cloud.*:
	# https://github.com/googleapis/google-cloud-python/issues/6742
	logging.getLogger().handlers = []
	logging.basicConfig(level=logging.INFO)

Which links to googleapis/google-cloud-python#6742, which was actually a long-ago fixed but in grpc: grpc/grpc#17017

We probably need to do the configuration for the integration with the Python stdlib logging: https://cloud.google.com/python/docs/reference/logging/3.11.0/std-lib-integration

#4044 also raised the possibility of "more detailed logging as to what exactly is accessing the secrets (run_id, uploader would be obvious — or maybe we should do this for all logging from the processor via a LoggerAdapter?)" — and that seems like a worthwhile thing to do. (We could even encode these as an operation, but idk if that makes sense.)

Tracing might also be worthwhile to consider, to understand the interaction between the main webapp API and the processor.