subsecond: Typed HotFn pointer (#4153)

* type the HotFn pointer

* can reuse a HotFnPtr to run a hot patched function

* unsafe constructor

* try_call_with_ptr is unsafe

packages/core/src/properties.rs

@@ -155,7 +155,7 @@ where
     }
 
     fn fn_ptr(&self) -> usize {
-        subsecond::HotFn::current(self.clone()).ptr_address() as usize
+        subsecond::HotFn::current(self.clone()).ptr_address().0 as usize
     }
 }
 
@@ -170,7 +170,7 @@ where
     }
 
     fn fn_ptr(&self) -> usize {
-        subsecond::HotFn::current(self.clone()).ptr_address() as usize
+        subsecond::HotFn::current(self.clone()).ptr_address().0 as usize
     }
 }