add Expected trait to utils; use (already transitive) num-traits.

Signed-off-by: Jason Volk <jason@zemos.net>

src/core/Cargo.toml

@@ -77,6 +77,7 @@ itertools.workspace = true
 libc.workspace = true
 libloading.workspace = true
 log.workspace = true
+num-traits.workspace = true
 rand.workspace = true
 regex.workspace = true
 reqwest.workspace = true