Add domain to all signature funcitons, modify validate_proof_of_possession()

eth2/fork_choice/src/slow_lmd_ghost.rs

@@ -29,7 +29,7 @@ use std::collections::HashMap;
 use std::sync::Arc;
 use types::{
     readers::{BeaconBlockReader, BeaconStateReader},
-    slot_epoch_height::Slot,
+    slot_epoch::Slot,
     validator_registry::get_active_validator_indices,
     BeaconBlock, Hash256,
 };