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>

common/validator_dir/src/validator_dir.rs

@@ -3,7 +3,7 @@ use crate::builder::{
     WITHDRAWAL_KEYSTORE_FILE, keystore_password_path,
 };
 use deposit_contract::decode_eth1_tx_data;
-use derivative::Derivative;
+use educe::Educe;
 use eth2_keystore::{Error as KeystoreError, Keystore, PlainText};
 use lockfile::{Lockfile, LockfileError};
 use std::fs::{File, read, write};
@@ -56,11 +56,11 @@ pub struct Eth1DepositData {
 ///
 /// Holds a lockfile in `self.dir` to attempt to prevent concurrent access from multiple
 /// processes.
-#[derive(Debug, Derivative)]
-#[derivative(PartialEq)]
+#[derive(Debug, Educe)]
+#[educe(PartialEq)]
 pub struct ValidatorDir {
     dir: PathBuf,
-    #[derivative(PartialEq = "ignore")]
+    #[educe(PartialEq(ignore))]
     _lockfile: Lockfile,
 }