allow for `u8` to be used as hold/freeze reason (#5348)

..without needing to provide your own `newtype` around it.  

This will allow `type Reason = u8` to be used as `FreezeReason` and
`HoldReason`, which I think is a nice simplification if one doens't want
to deal with the complications.

At the same time, it is a bit of an anti-pattern.

Putting it out there to check people's vibes.

prdoc/pr_5348.prdoc

+# Schema: Polkadot SDK PRDoc Schema (prdoc) v1.0.0
+# See doc at https://raw.githubusercontent.com/paritytech/polkadot-sdk/master/prdoc/schema_user.json
+
+title: allow for u8 to be used as hold/freeze reason
+
+doc:
+  - audience: Runtime Dev
+    description: |
+      Allows for `u8` type to be configured as `HoldReason` and `FreezeReason`
+
+crates:
+  - name: frame-support
+    bump: patch

substrate/frame/support/src/traits/misc.rs

@@ -48,6 +48,10 @@ impl VariantCount for () {
 	const VARIANT_COUNT: u32 = 0;
 }
 
+impl VariantCount for u8 {
+	const VARIANT_COUNT: u32 = 256;
+}
+
 /// Adapter for `Get<u32>` to access `VARIANT_COUNT` from `trait pub trait VariantCount {`.
 pub struct VariantCountOf<T: VariantCount>(core::marker::PhantomData<T>);
 impl<T: VariantCount> Get<u32> for VariantCountOf<T> {