Move state trans fns into state_processing

eth2/state_processing/src/common/exit_validator.rs

@@ -0,0 +1,22 @@
+use types::{BeaconStateError as Error, *};
+
+/// Exit the validator of the given `index`.
+///
+/// Spec v0.5.0
+pub fn exit_validator(
+    state: &mut BeaconState,
+    validator_index: usize,
+    spec: &ChainSpec,
+) -> Result<(), Error> {
+    if validator_index >= state.validator_registry.len() {
+        return Err(Error::UnknownValidator);
+    }
+
+    let delayed_epoch = state.get_delayed_activation_exit_epoch(state.current_epoch(spec), spec);
+
+    if state.validator_registry[validator_index].exit_epoch > delayed_epoch {
+        state.validator_registry[validator_index].exit_epoch = delayed_epoch;
+    }
+
+    Ok(())
+}