Fix tests on nightly (bytecodealliance#1999)

Ensure that `PartialOrd` and `Ord` implementations for `Alignment` are
the same instead of having one be manual and one be derived. This is
required to account for a small behavior change in nightly Rust.

crates/wit-parser/src/sizealign.rs

@@ -1,12 +1,13 @@
 use std::{
+    cmp::Ordering,
     num::NonZeroUsize,
     ops::{Add, AddAssign},
 };
 
 use crate::{FlagsRepr, Int, Resolve, Type, TypeDef, TypeDefKind};
 
 /// Architecture specific alignment
-#[derive(Eq, PartialEq, PartialOrd, Clone, Copy)]
+#[derive(Eq, PartialEq, Clone, Copy)]
 pub enum Alignment {
     /// This represents 4 byte alignment on 32bit and 8 byte alignment on 64bit architectures
     Pointer,
@@ -29,11 +30,17 @@ impl std::fmt::Debug for Alignment {
     }
 }
 
+impl PartialOrd for Alignment {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
 impl Ord for Alignment {
     /// Needed for determining the max alignment of an object from its parts.
     /// The ordering is: Bytes(1) < Bytes(2) < Bytes(4) < Pointer < Bytes(8)
     /// as a Pointer is either four or eight byte aligned, depending on the architecture
-    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
+    fn cmp(&self, other: &Self) -> Ordering {
         match (self, other) {
             (Alignment::Pointer, Alignment::Pointer) => std::cmp::Ordering::Equal,
             (Alignment::Pointer, Alignment::Bytes(b)) => {