[Feature] Profiling

[bungoboingo]

This PR introduces basic support for tracing as a feature of iced_winit. For now, only Chrome traces are supported, but I have plans to add support for Tracy in the near future!

Simply enable iced/chrome-trace feature to generate a trace file at the location of your current executable, e.g.:
target/debug(or release)/traces/package_trace_timestamp.json.

Any traces you include using the tracing crate will be included in addition to builtin things as frame time, application events, renderer draw calls for either wgpu or glow, etc.

E.g., in your application:

let _ = tracing::info_span!("MyTrace").entered(); // span ref dropped at end of scope

Chrome traces can be viewed at ui.perfetto.dev by opening the JSON file in the viewer.

Let me know what you think, thanks!

[bungoboingo]

Updated this re: a discussion on restructuring this to just be a simple feature of iced_winit.

Changes in 60f6e7b:

1. Removed iced_profiling crate, adjusted all dependencies to just rely on the base tracing crate.
2. Changed the location of generated trace files to be within the current executable's path.
3. Restructured features a bit for clarity/to avoid repetition.

[hecrj]

Looks great! Thanks 🙇