Adjust to upcoming world age change in Julia 1.12

Julia 1.12 will change where world age increments are being inserted
implicitly. The expansion of `@constinferred` is relying on an implicit
world age increment between `eval` and the subsequent evaluation, which
may go away in 1.12. Add an explicit marker to force the increment to
be retained here. This preserves existing behavior. It may be the case
that an alternative world age mechanism (e.g. invokelatest) is more
appropriate, but it's hard for me to evaluate without full context.

Author: Keno

src/constinferred.jl

@@ -41,7 +41,7 @@ testing type stability of a new function, where all arguments or keyword argumen
 the original function `f` that have a constant value (in the call expression) of type
 `Union{Number,Char,Symbol}` are hard coded.
 
-If you want to test for constant propagation in a variable which is not hard-coded in 
+If you want to test for constant propagation in a variable which is not hard-coded in
 the call expression, you can interpolate it into the expression.
 
 Secondly, @constinferred returns the value if type inference succeeds, like `@inferred`,
@@ -175,9 +175,11 @@ function _constinferred(ex, mod, src, test_f, allow=:(Union{}))
         end
         $result
     end
+    latestworld = isdefined(Core, :var"@latestworld") ? :(@Core.latestworld) : nothing
     finalex = Base.remove_linenums!(quote
                                         $pre
                                         Core.eval($mod, $fundefex)
+                                        $latestworld
                                         let
                                             $main
                                             $post