Add {fork_name}_enabled functions (#5951)

* add fork_name_enabled fn to Forkname impl

* refactor codebase to use new fork_enabled fn

* fmt

* Merge branch 'unstable' of https://github.com/sigp/lighthouse into fork-ord-impl

* small code cleanup

* resolve merge conflicts

* fix beacon chain test

* merge conflicts

* fix ef test issue

* resolve merge conflicts

beacon_node/beacon_chain/src/attestation_verification.rs

@@ -1144,13 +1144,14 @@ pub fn verify_propagation_slot_range<S: SlotClock, E: EthSpec>(
 
     let current_fork =
         spec.fork_name_at_slot::<E>(slot_clock.now().ok_or(BeaconChainError::UnableToReadSlot)?);
-    let earliest_permissible_slot = if !current_fork.deneb_enabled() {
-        one_epoch_prior
-    // EIP-7045
-    } else {
+
+    let earliest_permissible_slot = if current_fork.deneb_enabled() {
+        // EIP-7045
         one_epoch_prior
             .epoch(E::slots_per_epoch())
             .start_slot(E::slots_per_epoch())
+    } else {
+        one_epoch_prior
     };
 
     if attestation_slot < earliest_permissible_slot {