Add a `Trace` equivalent to extension's logging setting

[andyleejordan]

Noted in #1474, I think we should add a Trace equivalent to the extension's logging setting and our loose abstraction of PsesLogLevel. Notably, we're not sure right now how to get existing trace logs, and moreover, the assembly load events are super noisy and should be moved to a Trace level.

I think settings Diagnostics in the extension gets Trace logs because in the end that's an int with the value 0. Obviously we need to clean this up.

[andyleejordan]

Ah ha, got an answer. Microsoft.Extensions.Logging.LogLevel.Trace shows up as "Verbose" in out log emitter.