Remove the stack map registry.

This commit removes the stack map registry and instead uses the existing
information from the store's module registry to lookup stack maps.

A trait is now used to pass the lookup context to the runtime, implemented by
`Store` to do the lookup.

With this change, module registration in `Store` is now entirely limited to
inserting the module into the module registry.

crates/wasmtime/src/trampoline/func.rs

@@ -283,7 +283,7 @@ pub fn create_function(
                 host_state: Box::new(trampoline_state),
                 interrupts: std::ptr::null(),
                 externref_activations_table: std::ptr::null_mut(),
-                stack_map_registry: std::ptr::null_mut(),
+                stack_map_lookup: None,
             })?,
             trampoline,
         ))
@@ -315,7 +315,7 @@ pub unsafe fn create_raw_function(
             host_state,
             interrupts: std::ptr::null(),
             externref_activations_table: std::ptr::null_mut(),
-            stack_map_registry: std::ptr::null_mut(),
+            stack_map_lookup: None,
         })?,
     )
 }