Ensure TraceLogger log level is maintained property

[Youssef1313]

The added test would fail only under .NET Framework without the production change in this PR.

Under .NET Framework, if you execute the following:

new TraceSource("Default", SourceLevels.Warning).Switch.Level

it will produce -1 (corresponding to SourceLevels.All).

After Initialize gets called in TraceLogger constructor, the level is set as:

Level = MapLoggerLevel(traceSource.Switch.Level);

which used to set it to Trace, even when Warning is explicitly requested.

The caching in TraceLogger generally looks wrong to me though. It caches TraceSource per Name, not taking into account the fact that multiple TraceLogger might be requested with the same name but different levels.

[stakx]

To be honest, I'm not sure there's much sense in investing any more time and work in Castle logging facilities. Seems more likely to me that we're going to deprecate them soon (see the discussion in #408, plus Jono mentioned to me recently that Windsor hasn't seen much activity in recent times... so one fewer reason for keeping logging facilities going).

[Youssef1313]

@stakx Any expected time when they will be deprecated? And when 6.x is expected to be released?

Meanwhile, this bug is causing perf issues for Moq under .NET Framework. I think the scope of the change is small enough and should be safe to get in until the deprecation happens?