Move the signature registry into Engine.

This commit moves the shared signature registry out of `Store` and into
`Engine`.

This helps eliminate work that was performed whenever a `Module` was
instantiated into a `Store`.

Now a `Module` is registered with the shared signature registry upon creation,
storing the mapping from the module's signature index space to the shared index
space.

This also refactors the "frame info" registry into a general purpose "module
registry" that is used to look up trap information, signature information, and
(soon) stack map information.

crates/wasmtime/src/trampoline/func.rs

@@ -1,6 +1,6 @@
 //! Support for a calling of an imported function.
 
-use crate::{sig_registry::SignatureRegistry, Config, FuncType, Trap};
+use crate::{Config, FuncType, Store, Trap};
 use anyhow::Result;
 use std::any::Any;
 use std::cmp;
@@ -262,15 +262,15 @@ pub fn create_function(
     ft: &FuncType,
     func: Box<dyn Fn(*mut VMContext, *mut u128) -> Result<(), Trap>>,
     config: &Config,
-    registry: Option<&mut SignatureRegistry>,
+    store: Option<&Store>,
 ) -> Result<(InstanceHandle, VMTrampoline)> {
     let (module, finished_functions, trampoline, trampoline_state) =
         create_function_trampoline(config, ft, func)?;
 
-    // If there is no signature registry, use the default signature index which is
+    // If there is no store, use the default signature index which is
     // guaranteed to trap if there is ever an indirect call on the function (should not happen)
-    let shared_signature_id = registry
-        .map(|r| r.register(ft.as_wasm_func_type(), trampoline))
+    let shared_signature_id = store
+        .map(|s| s.register_signature(ft.as_wasm_func_type(), trampoline))
         .unwrap_or(VMSharedSignatureIndex::default());
 
     unsafe {