Expose getter/setter for EntityGeneration (#21101)

While the EntityGeneration has an opaque underlying structure; it can
still be useful to be able to access the actual value (for instance for
networking)

Do I need to add a Migration Guide?

Author: cBournhonesque

crates/bevy_ecs/src/entity/mod.rs

@@ -218,15 +218,15 @@ impl EntityGeneration {
     /// Gets some bits that represent this value.
     /// The bits are opaque and should not be regarded as meaningful.
     #[inline(always)]
-    const fn to_bits(self) -> u32 {
+    pub const fn to_bits(self) -> u32 {
         self.0
     }
 
     /// Reconstruct an [`EntityGeneration`] previously destructured with [`EntityGeneration::to_bits`].
     ///
     /// Only useful when applied to results from `to_bits` in the same instance of an application.
     #[inline]
-    const fn from_bits(bits: u32) -> Self {
+    pub const fn from_bits(bits: u32) -> Self {
         Self(bits)
     }