Use Self everywhere (#3787)

This turns on the clippy lint
[`clippy::use_self`](https://rust-lang.github.io/rust-clippy/v0.0.212/index.html#use_self)
and fixes it everywhere.

crates/emath/src/range.rs

@@ -71,7 +71,7 @@ impl Rangef {
     /// Flip `min` and `max` if needed, so that `min <= max` after.
     #[inline]
     pub fn as_positive(self) -> Self {
-        Rangef {
+        Self {
             min: self.min.min(self.max),
             max: self.min.max(self.max),
         }