Only insert or remove input if needed (#4273)

# Objective

We are currently inserting an `input` into `pressed` even if it is already pressed. This also applies to releasing an input. This is not a big deal, but since we are already checking if the `input` is pressed or not we might as well remove the cost of the value update caused by the `pressed.insert` method.

Related to #4209

## Solution

Only insert or remove input if needed.

crates/bevy_input/src/input.rs

@@ -51,11 +51,10 @@ where
 {
     /// Register a press for input `input`.
     pub fn press(&mut self, input: T) {
-        if !self.pressed(input) {
+        // Returns `true` if the `input` wasn't pressed.
+        if self.pressed.insert(input) {
             self.just_pressed.insert(input);
         }
-
-        self.pressed.insert(input);
     }
 
     /// Check if `input` has been pressed.
@@ -70,11 +69,10 @@ where
 
     /// Register a release for input `input`.
     pub fn release(&mut self, input: T) {
-        if self.pressed(input) {
+        // Returns `true` if the `input` was pressed.
+        if self.pressed.remove(&input) {
             self.just_released.insert(input);
         }
-
-        self.pressed.remove(&input);
     }
 
     /// Check if `input` has been just pressed.