Revise logging to be more useful

**Task description**

The current node logging does not serve any specific purpose very well. Some of the issues that routinely come up
- logs tend to get large quickly even in INFO mode
- we have found that INFO logging is of very very limited value when debugging issues
- on the other hand INFO logging is quite spammy, it logs each received block, printing a bunch of statistics for them, but at the same time does not log very clearly which block it produced itself (this has to be discerned from followup log items)
- DEBUG and TRACE logging are more useful for debugging issues, but many things are logged which are of dubious value, and on the other hand some are not. For example we do not log why transactions were rejected on the gRPC layer, and this would often be useful.
- some things that are logged as ERROR should probably not be that. For example failing to send on a connection is not really a critical error. It most likely means the peer disconnected.

This issue is meant to collect the various concrete improvements we could do to logging to make it more useful.

**Sub-tasks**
- [ ] Come to an agreement on what the purpose of the different logging levels is. The current situation is not really designed, it has grown and write a document describing the agreement.
- [ ] Make followup tasks to revise the logging according to the agreement.

No files, tests, or entry points are named. Start by defining the purpose of each logging level and documenting the agreement, then create follow-up tasks for the concrete logging changes; the issue is done when those decisions and follow-up tasks exist.

Written by the indexing model from the issue text.