Attestation processing (#497)

* Renamed fork_choice::process_attestation_from_block

* Processing attestation in fork choice

* Retrieving state from store and checking signature

* Looser check on beacon state validity.

* Cleaned up get_attestation_state

* Expanded fork choice api to provide latest validator message.

* Checking if the an attestation contains a latest message

* Correct process_attestation error handling.

* Copy paste error in comment fixed.

* Tidy ancestor iterators

* Getting attestation slot via helper method

* Refactored attestation creation in test utils

* Revert "Refactored attestation creation in test utils"

This reverts commit 4d277fe4239a7194758b18fb5c00dfe0b8231306.

* Integration tests for free attestation processing

* Implicit conflicts resolved.

* formatting

* Do first pass on Grants code

* Add another attestation processing test

* Tidy attestation processing

* Remove old code fragment

* Add non-compiling half finished changes

* Simplify, fix bugs, add tests for chain iters

* Remove attestation processing from op pool

* Fix bug with fork choice, tidy

* Fix overly restrictive check in fork choice.

* Ensure committee cache is build during attn proc

* Ignore unknown blocks at fork choice

* Various minor fixes

* Make fork choice write lock in to read lock

* Remove unused method

* Tidy comments

* Fix attestation prod. target roots change

* Fix compile error in store iters

* Reject any attestation prior to finalization

* Fix minor PR comments

* Remove duplicated attestation finalization check

* Remove awkward `let` statement

eth2/state_processing/src/per_block_processing.rs

@@ -15,8 +15,7 @@ pub use is_valid_indexed_attestation::{
     is_valid_indexed_attestation, is_valid_indexed_attestation_without_signature,
 };
 pub use verify_attestation::{
-    verify_attestation, verify_attestation_time_independent_only,
-    verify_attestation_without_signature,
+    verify_attestation_for_block_inclusion, verify_attestation_for_state,
 };
 pub use verify_deposit::{
     get_existing_validator_index, verify_deposit_merkle_proof, verify_deposit_signature,
@@ -37,6 +36,12 @@ mod verify_exit;
 mod verify_proposer_slashing;
 mod verify_transfer;
 
+#[derive(PartialEq)]
+pub enum VerifySignatures {
+    True,
+    False,
+}
+
 /// Updates the state for a new block, whilst validating that the block is valid.
 ///
 /// Returns `Ok(())` if the block is valid and the state was successfully updated. Otherwise
@@ -312,7 +317,8 @@ pub fn process_attestations<T: EthSpec>(
         .par_iter()
         .enumerate()
         .try_for_each(|(i, attestation)| {
-            verify_attestation(state, attestation, spec).map_err(|e| e.into_with_index(i))
+            verify_attestation_for_block_inclusion(state, attestation, spec, VerifySignatures::True)
+                .map_err(|e| e.into_with_index(i))
         })?;
 
     // Update the state in series.