fix(ci): 192 core spot runner (#5767)

The cpp parts really churn. Buy time for better solution with compute

.github/workflows/ci.yml

@@ -24,7 +24,7 @@ jobs:
       ebs_cache_size_gb: 256
       runner_concurrency: 50
       subaction: ${{ github.event.inputs.runner_action || 'start' }}
-      ec2_instance_type: m6a.32xlarge
+      ec2_instance_type: m6a.48xlarge
       ec2_ami_id: ami-04d8422a9ba4de80f
       ec2_instance_ttl: 40 # refreshed by jobs
     secrets: inherit
@@ -143,3 +143,9 @@ jobs:
         working-directory: ./barretenberg/cpp/
         timeout-minutes: 15
         run: earthly --no-output +bench-ultra-honk --bench_mode=cache
+
+  merge-check:
+    runs-on: ${{ github.actor }}-x86
+    needs: [e2e, bb-native-tests, bb-bench]
+    steps:
+      - run: echo Pull request merging now allowed.