Enable stdout/stderr logging by default on UWP

[jdm]

We currently disable logging in release builds unless the FirefoxRealityLogStdout environment variable is set. There's no good way to set such a variable on a HoloLens 2 without recompiling the app, which means it's effectively impossible to get logging out of an arbitrary user's build and they have to be provided a custom build instead. This sucks; we should log by default instead so they can always grab it from the app's local files if they encounter a problem. This will give us warn!/error! output and any println/eprintln, such as panic messages.