Migrate derivative to educe (#8125)

Fixes #7001.


  Mostly mechanical replacement of `derivative` attributes with `educe` ones.

### **Attribute Syntax Changes**

```rust
// Bounds: = "..." → (...)
#[derivative(Hash(bound = "E: EthSpec"))]
#[educe(Hash(bound(E: EthSpec)))]

// Ignore: = "ignore" → (ignore)
#[derivative(PartialEq = "ignore")]
#[educe(PartialEq(ignore))]

// Default values: value = "..." → expression = ...
#[derivative(Default(value = "ForkName::Base"))]
#[educe(Default(expression = ForkName::Base))]

// Methods: format_with/compare_with = "..." → method(...)
#[derivative(Debug(format_with = "fmt_peer_set_as_len"))]
#[educe(Debug(method(fmt_peer_set_as_len)))]

// Empty bounds: removed entirely, educe can infer appropriate bounds
#[derivative(Default(bound = ""))]
#[educe(Default)]

// Transparent debug: manual implementation (educe doesn't support it)
#[derivative(Debug = "transparent")]
// Replaced with manual Debug impl that delegates to inner field
```

**Note**: Some bounds use strings (`bound("E: EthSpec")`) for superstruct compatibility (`expected ','` errors).


Co-Authored-By: Javier Chávarri <javier.chavarri@gmail.com>

Co-Authored-By: Mac L <mjladson@pm.me>

beacon_node/beacon_chain/src/sync_committee_verification.rs

@@ -31,7 +31,7 @@ use crate::{
     BeaconChain, BeaconChainError, BeaconChainTypes, metrics, observed_aggregates::ObserveOutcome,
 };
 use bls::{PublicKeyBytes, verify_signature_sets};
-use derivative::Derivative;
+use educe::Educe;
 use safe_arith::ArithError;
 use slot_clock::SlotClock;
 use ssz_derive::{Decode, Encode};
@@ -261,8 +261,8 @@ impl From<ContributionError> for Error {
 }
 
 /// Wraps a `SignedContributionAndProof` that has been verified for propagation on the gossip network.\
-#[derive(Derivative)]
-#[derivative(Clone(bound = "T: BeaconChainTypes"))]
+#[derive(Educe)]
+#[educe(Clone(bound(T: BeaconChainTypes)))]
 pub struct VerifiedSyncContribution<T: BeaconChainTypes> {
     signed_aggregate: SignedContributionAndProof<T::EthSpec>,
     participant_pubkeys: Vec<PublicKeyBytes>,