Fix unit test for SPR-11919

Issue: SPR-11919
Fine tune STOMP and WebSocket related logging

Optimize logging with tracking the opening and closing of WebSocket
sessions and STOMP broker connections in mind.

While the volume of messages makes it impractical to log every message
at anything higher than TRACE, the opening and closing of connections
is more manageable and can be logged at INFO. This makes it possible to
drop to INFO in production and get useful information without getting
too much in a short period of time.

The logging is also optimized to avoid providing the same information
from multiple places since messages pass through multiple layers.

Issue: SPR-11884
Nested properties support for field-based validation

This commit validates that the changes introduced in 8221c9abc5 are
indeed allowing DirectFieldBindingResult to support nested validation
paths.

Issue: SPR-10623
Fix warning