fix(core): add missing bounds to type-alias-impl-traits

It seems that [rust-lang/rust#96736][1] introduced checks for these
missing bounds, resulting in the following compilation error:

     error[E0277]: expected a `FnOnce<(Output,)>` closure, found `Mapper`
         --> src/r3_core/src/bind.rs:1360:5
          |
     1360 |     move || (mapper)(inner_bound_fn())
          |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected an `FnOnce<(Output,)>` closure, found `Mapper`
          |
     note: required by a bound in `map_bind_inner`
         --> src/r3_core/src/bind.rs:1358:13
          |
     1352 | const fn map_bind_inner<InnerBoundFn, Output, Mapper, NewOutput>(
          |          -------------- required by a bound in this
     ...
     1358 |     Mapper: FnOnce(Output) -> NewOutput + Copy + Send + 'static,
          |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `map_bind_inner`
     help: consider further restricting this bound
          |
     1349 |     Mapper: Copy + Send + 'static + core::ops::FnOnce<(Output,)>,
          |                                   ++++++++++++++++++++++++++++++

[1]: rust-lang/rust#96736

Author: yvt

src/r3_core/src/bind.rs

@@ -1216,7 +1216,8 @@ macro_rules! impl_fn_bind {
             type BoundFn<T, Output, $( $RuntimeBinderI, )*>
             where
                 $( $RuntimeBinderI: RuntimeBinder, )*
-                T: Copy + Send + 'static,
+                T: for<'call> FnOnce($( $RuntimeBinderI::Target<'call>, )*)
+                    -> Output + Copy + Send + 'static,
              = impl FnOnce() -> Output + Copy + Send + 'static;
 
             const fn bind_inner<
@@ -1345,8 +1346,8 @@ where
 
 type MappedBoundFn<InnerBoundFn, Output, Mapper, NewOutput>
 where
-    InnerBoundFn: Copy + Send + 'static,
-    Mapper: Copy + Send + 'static,
+    InnerBoundFn: FnOnce() -> Output + Copy + Send + 'static,
+    Mapper: FnOnce(Output) -> NewOutput + Copy + Send + 'static,
 = impl FnOnce() -> NewOutput + Copy + Send + 'static;
 
 const fn map_bind_inner<InnerBoundFn, Output, Mapper, NewOutput>(