Position persistence and sane clamping to still-available monitors for Windows (#2583)

* Attempt to fix monitor clamping on Windows so window positions can be restored between sessions.

* Missed a change.

* Renamed variables, reorganized some lines of code, and added some more comments.

* Cargo fmt run

* Updated CHANGELOG.md to briefly describe my change

* Updated CHANGELOG.md to briefly describe my change

* Applied suggested fixes from emilk
Discovered an issue where putting the monitor off a non-primary monitor to the left causes the position to be off the monitor x and y range, clamping to the primary instead of the non-primary.

* Fix for matching negative restored window positions. Should clamp if any part of the window had been visible on a remaining monitor.

* Apparently compiler attributes on statements have been marked unstable.
Rather than just wrap in blocks, I kind of prefer the more explicit if cfg! call for line 114.

CHANGELOG.md - correct a missing paren I noticed

* I was being silly, I don't need to clone inner_size_points on line 112

* Cargo fmt run

* Update crates/egui-winit/CHANGELOG.md

emilk suggested changelog formatting

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

* Update window_settings.rs

Satisfy CI Error

* clippy

---------

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

crates/egui-winit/CHANGELOG.md

@@ -3,6 +3,7 @@ All notable changes to the `egui-winit` integration will be noted in this file.
 
 
 ## Unreleased
+* Fixed window position persistence for Windows ([#2583](https://github.com/emilk/egui/issues/2583)).
 * Update to `winit` 0.28, adding support for mac trackpad zoom ([#2654](https://github.com/emilk/egui/pull/2654)).
 * Remove the `screen_reader` feature. Use the `accesskit` feature flag instead ([#2669](https://github.com/emilk/egui/pull/2669)).