Migrate custom size/position types to those from the dpi crate

[prokopyl]

This PR removes the WindowInfo, Size, Point, PhySize and PhyPoint types, and replaces them with types from the dpi crate.

This provides usability improvements compared to the old types, as well as better ecosystem integration (since those types are used widely in the Rust GUI ecosystem).

This change also enables a couple more improvements, which this PR provides:

• Use the dpi::Size type in WindowOpenOptions::size and WindowContext::resize, allowing users to pass either physical or logical sizes.
• Move the WindowEvent::Resized event to its own WindowContext::resized handler, properly indicating that window resizes are not an event that can be captured or ignored.
• Introduce a new WindowSize type used in the resized handler, providing both physical and logical sizes with the guarantee that one of them came directly from the underlying platform APIs. This prevents having to do back-and-forth conversions that can be lossy due to rounding.