Rename random to prev_randao (#3040)

## Issue Addressed

As discussed on last-night's consensus call, the testnets next week will target the [Kiln Spec v2](https://hackmd.io/@n0ble/kiln-spec).

Presently, we support Kiln V1. V2 is backwards compatible, except for renaming `random` to `prev_randao` in:

- https://github.com/ethereum/execution-apis/pull/180
- https://github.com/ethereum/consensus-specs/pull/2835

With this PR we'll no longer be compatible with the existing Kintsugi and Kiln testnets, however we'll be ready for the testnets next week. I raised this breaking change in the call last night, we are all keen to move forward and break things.

We now target the [`merge-kiln-v2`](https://github.com/MariusVanDerWijden/go-ethereum/tree/merge-kiln-v2) branch for interop with Geth. This required adding the `--http.aauthport` to the tester to avoid a port conflict at startup.

### Changes to exec integration tests

There's some change in the `merge-kiln-v2` version of Geth that means it can't compile on a vanilla Github runner. Bumping the `go` version on the runner solved this issue.

Whilst addressing this, I refactored the `testing/execution_integration` crate to be a *binary* rather than a *library* with tests. This means that we don't need to run the `build.rs` and build Geth whenever someone runs `make lint` or `make test-release`. This is nice for everyday users, but it's also nice for CI so that we can have a specific runner for these tests and we don't need to ensure *all* runners support everything required to build all execution clients.

## More Info

- [x] ~~EF tests are failing since the rename has broken some tests that reference the old field name. I have been told there will be new tests released in the coming days (25/02/22 or 26/02/22).~~

beacon_node/beacon_chain/src/execution_payload.rs

@@ -12,7 +12,7 @@ use crate::{
     ExecutionPayloadError,
 };
 use execution_layer::PayloadStatus;
-use fork_choice::PayloadVerificationStatus;
+use fork_choice::{InvalidationOperation, PayloadVerificationStatus};
 use proto_array::{Block as ProtoBlock, ExecutionStatus};
 use slog::debug;
 use slot_clock::SlotClock;
@@ -68,7 +68,13 @@ pub fn notify_new_payload<T: BeaconChainTypes>(
                 // This block has not yet been applied to fork choice, so the latest block that was
                 // imported to fork choice was the parent.
                 let latest_root = block.parent_root();
-                chain.process_invalid_execution_payload(latest_root, Some(latest_valid_hash))?;
+                chain.process_invalid_execution_payload(
+                    &InvalidationOperation::InvalidateMany {
+                        head_block_root: latest_root,
+                        always_invalidate_head: false,
+                        latest_valid_ancestor: latest_valid_hash,
+                    },
+                )?;
 
                 Err(ExecutionPayloadError::RejectedByExecutionEngine { status }.into())
             }
@@ -145,11 +151,19 @@ pub fn validate_merge_block<T: BeaconChainTypes>(
                 .slot_clock
                 .now()
                 .ok_or(BeaconChainError::UnableToReadSlot)?;
-            // Check the optimistic sync conditions. Note that because this is the merge block,
-            // the justified checkpoint can't have execution enabled so we only need to check the
-            // current slot is at least SAFE_SLOTS_TO_IMPORT_OPTIMISTICALLY ahead of the block
-            // https://github.com/ethereum/consensus-specs/blob/v1.1.9/sync/optimistic.md#when-to-optimistically-import-blocks
-            if block.slot() + chain.spec.safe_slots_to_import_optimistically <= current_slot {
+
+            // Ensure the block is a candidate for optimistic import.
+            if chain
+                .fork_choice
+                .read()
+                .is_optimistic_candidate_block(
+                    current_slot,
+                    block.slot(),
+                    &block.parent_root(),
+                    &chain.spec,
+                )
+                .map_err(BeaconChainError::from)?
+            {
                 debug!(
                     chain.log,
                     "Optimistically accepting terminal block";