chore: assert as-sha256 is used as hasher by ssz (#7394)

**Motivation**

Loading an incorrect hasher can cause strange regressions in performance
which might not be immediately obvious, best to catch this at startup
and exit as there is no reason for the beacon node to use any other
hasher besides as-sha256 (at least right now).

**Description**

Assert as-sha256 is used as hasher by ssz

Author: nflaig

packages/cli/src/cmds/beacon/handler.ts

@@ -1,5 +1,6 @@
 import path from "node:path";
 import {getHeapStatistics} from "node:v8";
+import {hasher} from "@chainsafe/persistent-merkle-tree";
 import {BeaconDb, BeaconNode} from "@lodestar/beacon-node";
 import {ChainForkConfig, createBeaconConfig} from "@lodestar/config";
 import {LevelDbController} from "@lodestar/db";
@@ -36,6 +37,10 @@ const EIGHT_GB = 8 * 1024 * 1024 * 1024;
 export async function beaconHandler(args: BeaconArgs & GlobalArgs): Promise<void> {
   const {config, options, beaconPaths, network, version, commit, peerId, logger} = await beaconHandlerInit(args);
 
+  if (hasher.name !== "as-sha256") {
+    throw Error(`Loaded incorrect hasher ${hasher.name}, expected as-sha256`);
+  }
+
   const heapSizeLimit = getHeapStatistics().heap_size_limit;
   if (heapSizeLimit < EIGHT_GB) {
     logger.warn(