feat: allow state in HookSet

This is quite useful for example when doing statement coverage. One
could store a MPSC tx end inside a BranchHookSet in order to send the
current program counter on every branching instruction. Stateless are
still possible and should be zero cost, they can be implemented by just
using an empty struct on which the HookSet trait is implemented.

src/execution/mod.rs

@@ -1,5 +1,3 @@
-use core::marker::PhantomData;
-
 use alloc::vec::Vec;
 
 use value_stack::Stack;
@@ -35,20 +33,20 @@ where
     wasm_bytecode: &'b [u8],
     types: Vec<FuncType>,
     store: Store,
-    hook_set: PhantomData<H>,
+    pub hook_set: H,
 }
 
 impl<'b> RuntimeInstance<'b, EmptyHookSet> {
     pub fn new(validation_info: &'_ ValidationInfo<'b>) -> Result<Self> {
-        Self::new_with_hooks(validation_info)
+        Self::new_with_hooks(validation_info, EmptyHookSet)
     }
 }
 
 impl<'b, H> RuntimeInstance<'b, H>
 where
     H: HookSet,
 {
-    pub fn new_with_hooks(validation_info: &'_ ValidationInfo<'b>) -> Result<Self> {
+    pub fn new_with_hooks(validation_info: &'_ ValidationInfo<'b>, hook_set: H) -> Result<Self> {
         trace!("Starting instantiation of bytecode");
 
         let store = Self::init_store(validation_info);
@@ -57,7 +55,7 @@ where
             wasm_bytecode: validation_info.wasm,
             types: validation_info.types.clone(),
             store,
-            hook_set: PhantomData,
+            hook_set,
         };
 
         if let Some(start) = validation_info.start {