message: Make ValueLike have Serialize
  Summary: True for both Value and FrozenValue, so useful to have.
diff: @@ -935,7 +935,14 @@ impl Serialize for FrozenValue {
  /// For details about each function, see the documentation for [`Value`],
  /// which provides the same functions (and more).
  pub trait ValueLike<'v>:
  - Eq + Copy + Debug + Default + Display + CoerceKey<Value<'v>> + Freeze<Frozen = FrozenValue>
  + Eq
  + + Copy
  + + Debug
  + + Default
  + + Display
  + + Serialize
  + + CoerceKey<Value<'v>>
  + + Freeze<Frozen = FrozenValue>
  {
  /// `StringValue` or `FrozenStringValue`.
  type String: StringValueLike<'v>;
  