A Window can now be resizable in only one direction (#4155)

For instance: `Window::new(…).resizable([true, false])` is a window that
is only resizable in the horizontal direction.

This PR also removes a hack added in
https://github.com/emilk/egui/pull/3039 which is no longer needed since
https://github.com/emilk/egui/pull/4026

crates/emath/src/vec2b.rs

@@ -19,6 +19,30 @@ impl Vec2b {
     pub fn any(&self) -> bool {
         self.x || self.y
     }
+
+    /// Are both `x` and `y` true?
+    #[inline]
+    pub fn all(&self) -> bool {
+        self.x && self.y
+    }
+
+    #[inline]
+    pub fn and(&self, other: impl Into<Self>) -> Self {
+        let other = other.into();
+        Self {
+            x: self.x && other.x,
+            y: self.y && other.y,
+        }
+    }
+
+    #[inline]
+    pub fn or(&self, other: impl Into<Self>) -> Self {
+        let other = other.into();
+        Self {
+            x: self.x || other.x,
+            y: self.y || other.y,
+        }
+    }
 }
 
 impl From<bool> for Vec2b {