Make all lines and rectangles crisp (#5518)

* Merge this first: https://github.com/emilk/egui/pull/5517

This aligns all rectangles and (horizontal or vertical) line segments to
the physical pixel grid in the `epaint::Tessellator`, making these
shapes appear crisp everywhere.

* Closes https://github.com/emilk/egui/issues/5164
* Closes https://github.com/emilk/egui/issues/3667

This undoes a lot of the explicit, egui-side aligning added in:
* https://github.com/emilk/egui/pull/4943

The new approach has several benefits over the old one:

* It is done automatically by epaint, so it is applied to everything (no
longer opt-in)
* It is applied after any layer transforms (so it always works)
* It makes line segments crisper on high-DPI screens
* All filled rectangles now has sides that end on pixel boundaries

examples/hello_android/Cargo.toml

@@ -4,7 +4,7 @@ version = "0.1.0"
 authors = ["Emil Ernerfeldt <emil.ernerfeldt@gmail.com>"]
 license = "MIT OR Apache-2.0"
 edition = "2021"
-rust-version = "1.76"
+rust-version = "1.80"
 publish = false
 
 # `unsafe_code` is required for `#[no_mangle]`, disable workspace lints to workaround lint error.
@@ -16,10 +16,7 @@ crate-type = ["cdylib"]
 
 
 [dependencies]
-eframe = { workspace = true, features = [
-    "default",
-    "android-native-activity",
-] }
+eframe = { workspace = true, features = ["default", "android-native-activity"] }
 
 # For image support:
 egui_extras = { workspace = true, features = ["default", "image"] }
@@ -29,4 +26,4 @@ winit = { workspace = true }
 android_logger = "0.14"
 
 [package.metadata.android]
-build_targets = [ "armv7-linux-androideabi", "aarch64-linux-android" ]
+build_targets = ["armv7-linux-androideabi", "aarch64-linux-android"]