[bevy_core/bytes] Fix UB with accessing memory with incorrect alignment (bevyengine#1966)

After running `bevy_core` through `miri`, errors were reported surrounding incorrect memory accesses within the `bytes` test suit. 

Specifically:
```
test bytes::tests::test_array_round_trip ... error: Undefined Behavior: accessing memory with alignment 1, but alignment 4 is required
   --> crates/bevy_core/src/bytes.rs:55:13
    |
55  |             (*ptr).clone()
    |             ^^^^^^ accessing memory with alignment 1, but alignment 4 is required
    |
```

and 

```
test bytes::tests::test_vec_bytes_round_trip ... error: Undefined Behavior: accessing memory with alignment 2, but alignment 4 is required
   --> /home/nward/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/slice/raw.rs:95:14
    |
95  |     unsafe { &*ptr::slice_from_raw_parts(data, len) }
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ accessing memory with alignment 2, but alignment 4 is required
    |
```

Solution:

The solution is to use `slice::align_to` method to ensure correct alignment.

Author: NathanSWard

crates/bevy_core/src/bytes.rs

@@ -46,14 +46,16 @@ pub trait FromBytes {
 
 impl<T> FromBytes for T
 where
-    T: Byteable + Clone,
+    T: Byteable + Copy,
 {
     fn from_bytes(bytes: &[u8]) -> Self {
-        unsafe {
-            let byte_ptr = bytes.as_ptr();
-            let ptr = byte_ptr as *const Self;
-            (*ptr).clone()
-        }
+        assert_eq!(
+            bytes.len(),
+            std::mem::size_of::<T>(),
+            "Cannot convert byte slice `&[u8]` to type `{}`. They are not the same size.",
+            std::any::type_name::<T>()
+        );
+        unsafe { bytes.as_ptr().cast::<T>().read_unaligned() }
     }
 }
 
@@ -62,7 +64,7 @@ where
     T: Byteable,
 {
     fn as_bytes(&self) -> &[u8] {
-        let len = std::mem::size_of_val(self);
+        let len = std::mem::size_of::<T>();
         unsafe { core::slice::from_raw_parts(self as *const Self as *const u8, len) }
     }
 }
@@ -166,15 +168,23 @@ where
 
 impl<T> FromBytes for Vec<T>
 where
-    T: Sized + Clone + Byteable,
+    T: Sized + Copy + Byteable,
 {
     fn from_bytes(bytes: &[u8]) -> Self {
+        assert_eq!(
+            bytes.len() % std::mem::size_of::<T>(),
+            0,
+            "Cannot convert byte slice `&[u8]` to type `Vec<{0}>`. Slice length is not a multiple of std::mem::size_of::<{0}>.",
+            std::any::type_name::<T>(),
+        );
+
+        let len = bytes.len() / std::mem::size_of::<T>();
+        let mut vec = Vec::<T>::with_capacity(len);
         unsafe {
-            let byte_ptr = bytes.as_ptr() as *const T;
-            let len = bytes.len() / std::mem::size_of::<T>();
-            let slice = core::slice::from_raw_parts::<T>(byte_ptr, len);
-            slice.to_vec()
+            std::ptr::copy_nonoverlapping(bytes.as_ptr(), vec.as_mut_ptr() as *mut u8, bytes.len());
+            vec.set_len(len);
         }
+        vec
     }
 }