Add ExportableDataPayload::eq_dyn

[sffc]

Toward #2683

[sffc]

The build failure is because I need to add more PartialEq impls. Good news is it seems I need only these 6:

error[E0277]: can't compare `icu_list::provider::ListFormatterPatternsV1<'a>` with `icu_list::provider::ListFormatterPatternsV1<'a>`

error[E0277]: can't compare `icu_properties::provider::names::PropertyValueNameToEnumMapV1<'a>` with `icu_properties::provider::names::PropertyValueNameToEnumMapV1<'a>`

error[E0277]: can't compare `icu_properties::provider::names::PropertyEnumToValueNameLinearMapV1<'a>` with `icu_properties::provider::names::PropertyEnumToValueNameLinearMapV1<'a>`

error[E0277]: can't compare `icu_properties::provider::names::PropertyEnumToValueNameSparseMapV1<'a>` with `icu_properties::provider::names::PropertyEnumToValueNameSparseMapV1<'a>`

error[E0277]: can't compare `icu_properties::provider::names::PropertyEnumToValueNameLinearTiny4MapV1<'a>` with `icu_properties::provider::names::PropertyEnumToValueNameLinearTiny4MapV1<'a>`

error[E0277]: can't compare `WeekDataV1` with `WeekDataV1`