```
A few changes to -debug=net logging:
- always log when disconnecting a peer
- only log various connection errors when -debug=net is enabled, since errors from random untrusted peers is completely expected
- log when ignoring a message due to violating protocol (primarily to make it easier to debug other implementations)
- use "peer=123" rather than "from 123" to make grepping logs a bit easier
- log the value of the bip-37 fRelay field in version messages both when sending and receiving a version message
```
Some differences from the source material are due to segwit and out of order backports.
Backport of core#20724.
Ref T1696.