Remove custom signal handler restrictions (#1843)

* remove custom signal handler origin restriction

* add a test for handling signals from a hostcall

* cargo fmt

crates/runtime/src/traphandlers.rs

@@ -589,11 +589,6 @@ impl<'a> CallThreadState<'a> {
             return ptr::null();
         }
 
-        // If this fault wasn't in wasm code, then it's not our problem
-        if !(self.is_wasm_code)(pc as usize) {
-            return ptr::null();
-        }
-
         // First up see if any instance registered has a custom trap handler,
         // in which case run them all. If anything handles the trap then we
         // return that the trap was handled.
@@ -603,6 +598,11 @@ impl<'a> CallThreadState<'a> {
             }
         }
 
+        // If this fault wasn't in wasm code, then it's not our problem
+        if !(self.is_wasm_code)(pc as usize) {
+            return ptr::null();
+        }
+
         // TODO: stack overflow can happen at any random time (i.e. in malloc()
         // in memory.grow) and it's really hard to determine if the cause was
         // stack overflow and if it happened in WebAssembly module.