Deduplicate some size/align calculations (#4658)

This commit is an effort to reduce the amount of complexity around
managing the size/alignment calculations of types in the canonical ABI.
Previously the logic for the size/alignment of a type was spread out
across a number of locations. While each individual calculation is not
really the most complicated thing in the world having the duplication in
so many places was constantly worrying me.

I've opted in this commit to centralize all of this within the runtime
at least, and now there's only one "duplicate" of this information in
the fuzzing infrastructure which is to some degree less important to
deduplicate. This commit introduces a new `CanonicalAbiInfo` type to
house all abi size/align information for both memory32 and memory64.
This new type is then used pervasively throughout fused adapter
compilation, dynamic `Val` management, and typed functions. This type
was also able to reduce the complexity of the macro-generated code
meaning that even `wasmtime-component-macro` is performing less math
than it was before.

One other major feature of this commit is that this ABI information is
now saved within a `ComponentTypes` structure. This avoids recursive
querying of size/align information frequently and instead effectively
caching it. This was a worry I had for the fused adapter compiler which
frequently sought out size/align information and would recursively
descend each type tree each time. The `fact-valid-module` fuzzer is now
nearly 10x faster in terms of iterations/s which I suspect is due to
this caching.

crates/component-util/src/lib.rs

@@ -1,5 +1,5 @@
 /// Represents the possible sizes in bytes of the discriminant of a variant type in the component model
-#[derive(Debug, Copy, Clone)]
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
 pub enum DiscriminantSize {
     /// 8-bit discriminant
     Size1,
@@ -11,7 +11,7 @@ pub enum DiscriminantSize {
 
 impl DiscriminantSize {
     /// Calculate the size of discriminant needed to represent a variant with the specified number of cases.
-    pub fn from_count(count: usize) -> Option<Self> {
+    pub const fn from_count(count: usize) -> Option<Self> {
         if count <= 0xFF {
             Some(Self::Size1)
         } else if count <= 0xFFFF {
@@ -22,16 +22,21 @@ impl DiscriminantSize {
             None
         }
     }
+
+    /// Returns the size, in bytes, of this discriminant
+    pub const fn byte_size(&self) -> u32 {
+        match self {
+            DiscriminantSize::Size1 => 1,
+            DiscriminantSize::Size2 => 2,
+            DiscriminantSize::Size4 => 4,
+        }
+    }
 }
 
 impl From<DiscriminantSize> for u32 {
     /// Size of the discriminant as a `u32`
     fn from(size: DiscriminantSize) -> u32 {
-        match size {
-            DiscriminantSize::Size1 => 1,
-            DiscriminantSize::Size2 => 2,
-            DiscriminantSize::Size4 => 4,
-        }
+        size.byte_size()
     }
 }
 
@@ -60,7 +65,7 @@ pub enum FlagsSize {
 
 impl FlagsSize {
     /// Calculate the size needed to represent a value with the specified number of flags.
-    pub fn from_count(count: usize) -> FlagsSize {
+    pub const fn from_count(count: usize) -> FlagsSize {
         if count == 0 {
             FlagsSize::Size0
         } else if count <= 8 {
@@ -74,7 +79,7 @@ impl FlagsSize {
 }
 
 /// Divide `n` by `d`, rounding up in the case of a non-zero remainder.
-fn ceiling_divide(n: usize, d: usize) -> usize {
+const fn ceiling_divide(n: usize, d: usize) -> usize {
     (n + d - 1) / d
 }