dusk-core: add serde support

[d-sonuga]

This is to add the feature described in #2773.
I've only added serde support for a single event struct - MoonlightTransactionEvent.
I need some thoughts on whether what I have now is okay.

I've added serde support for the event structs.
I also addedPartialEq derive impls for SlashEvent and StakeEvent so that they could be compared in tests.
Changed dusk-jubjub and bls12_381-bls versions to the ones that now have serde support.

[moCello]

Is there a reason why the traits are re-implemented for each type?
You might also be able to simply derive types that are composed of other types that implement Serialize and Deserialize already:
For example for StakeFundOwner adding this on top of its declaration will be enough:

#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub enum StakeFundOwner {
...
}

This is probably true for many other types as well.

[d-sonuga]

Is there a reason why the traits are re-implemented for each type? You might also be able to simply derive types that are composed of other types that implement Serialize and Deserialize already: For example for StakeFundOwner adding this on top of its declaration will be enough:

#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub enum StakeFundOwner {
...
}

This is probably true for many other types as well.

The reason is to keep all implementations in one place, for ease of auditing. I think @Neotamandua mentioned something about this at some point before?

Edit: the re-implementations aren't needed.

[moCello]

Looks good from my side.
But please wait for a go from @ZER0 and @Neotamandua as well as they are the ones that can judge the serialization approach.