Adds a new `IPluginLog` service to Dalamud, which provides scoped logging on a per-plugin basis. This improves log performance for plugins, and paves the way for per-plugin log levels.
* Plugins must opt in to enable verbose logging by setting `IPluginLog.MinimumLogLevel` to `LogEventLevel.Verbose`. This option is automatically enabled for dev plugins and is currently not persisted.
* All release plugins will default to `Debug` as their lowest allowed log level.
* This setting does not override the global log level set in Dalamud.