Added finish method for timer (#20154)

# Objective

- Add an easy way to finish a Timer

## Solution

- Tick the timer by the remaining time

## Testing

I have not tested, but it should work
---

## Showcase

```rust
let mut timer = Timer::from_seconds(1.5, TimerMode::Once);
timer.finish();
assert_eq!(timer.remaining(), Duration::from_secs(0))
```

---------

Co-authored-by: Jan Hohenheim <jan@hohenheim.ch>
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>

Author: 3 people

crates/bevy_time/src/timer.rs

@@ -220,6 +220,21 @@ impl Timer {
         self.duration = duration;
     }
 
+    /// Finishes the timer.
+    ///
+    /// # Examples
+    /// ```
+    /// # use bevy_time::*;
+    /// let mut timer = Timer::from_seconds(1.5, TimerMode::Once);
+    /// timer.finish();
+    /// assert!(timer.finished());
+    /// ```
+    #[inline]
+    pub fn finish(&mut self) {
+        let remaining = self.remaining();
+        self.tick(remaining);
+    }
+
     /// Returns the mode of the timer.
     ///
     /// # Examples