Event and Lifecycle spans should not be INFO level

[NickLarsenNZ]

These cause a lot of noise when implementing tracing output:

druid/druid/src/window.rs

Line 288 in 94b6ce5

let _span = info_span!("event");

druid/druid/src/core.rs

Line 418 in dda0073

info_span!("lifecycle")

For example, when I move the mouse across the Window, a tonne of INFO level logs are outputted. I think these should be TRACE due to how noisy they can be. Note: some of the events are indeed TRACE.

[cmyr]

Something else that might be useful is to allow the user to pass a tracing level to the debug tracer, e.g. you would do,

AppLauncher::with_window(my_window)
    .log_to_console(LevelFilter::DEBUG)