Fix Entity Debug Format (#14539)

# Objective

Fixes #12139

## Solution

See this comment on original issue for my proposal:
https://github.com/bevyengine/bevy/issues/12139#issuecomment-2241915791

This PR is an implementation of this proposal.

I modified the implementation of `fmt::Debug` to instead display
`0v0#12345` to ensure entity index, generation, and raw bits are all
present in the output for debug purposes while still keeping log message
concise.

`fmt::Display` remains as is (`0v0`) to offer an even shorter output.

To me, this is the most non-intrusive fix for this issue.

## Testing

Add `fn entity_debug` test

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
Co-authored-by: Gino Valente <49806985+MrGVSV@users.noreply.github.com>

crates/bevy_ecs/src/entity/mod.rs

@@ -142,7 +142,7 @@ type IdCursor = isize;
 /// [`Query::get`]: crate::system::Query::get
 /// [`World`]: crate::world::World
 /// [SemVer]: https://semver.org/
-#[derive(Clone, Copy, Debug)]
+#[derive(Clone, Copy)]
 #[cfg_attr(feature = "bevy_reflect", derive(Reflect))]
 #[cfg_attr(feature = "bevy_reflect", reflect_value(Hash, PartialEq))]
 #[cfg_attr(
@@ -390,6 +390,42 @@ impl<'de> Deserialize<'de> for Entity {
     }
 }
 
+/// Outputs the full entity identifier, including the index, generation, and the raw bits.
+///
+/// This takes the format: `{index}v{generation}#{bits}`.
+///
+/// # Usage
+///
+/// Prefer to use this format for debugging and logging purposes. Because the output contains
+/// the raw bits, it is easy to check it against serialized scene data.
+///
+/// Example serialized scene data:
+/// ```text
+/// (
+///   ...
+///   entities: {
+///     4294967297: (  <--- Raw Bits
+///       components: {
+///         ...
+///       ),
+///   ...
+/// )
+/// ```
+impl fmt::Debug for Entity {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(
+            f,
+            "{}v{}#{}",
+            self.index(),
+            self.generation(),
+            self.to_bits()
+        )
+    }
+}
+
+/// Outputs the short entity identifier, including the index and generation.
+///
+/// This takes the format: `{index}v{generation}`.
 impl fmt::Display for Entity {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "{}v{}", self.index(), self.generation())
@@ -1152,6 +1188,15 @@ mod tests {
         }
     }
 
+    #[test]
+    fn entity_debug() {
+        let entity = Entity::from_raw(42);
+        let string = format!("{:?}", entity);
+        assert!(string.contains("42"));
+        assert!(string.contains("v1"));
+        assert!(string.contains(format!("#{}", entity.to_bits()).as_str()));
+    }
+
     #[test]
     fn entity_display() {
         let entity = Entity::from_raw(42);