fix: do not trigger builder circuit breaker if clock slot < slots present (#7481)

**Motivation**

We currently disable the builder flow for the most part of epoch 0
because the circuit breaker is triggered and we fall back to local block
building. However the current check does not make much sense if there
were not enough slots yet where proposal could be included on-chain.

**Description**

Do not trigger builder circuit breaker if clock slot < slots present
(based on fork choice)

Author: nflaig

packages/beacon-node/src/chain/chain.ts

@@ -1212,7 +1212,7 @@ export class BeaconChain implements IBeaconChain {
       const {faultInspectionWindow, allowedFaults} = executionBuilder;
       const slotsPresent = this.forkChoice.getSlotsPresent(clockSlot - faultInspectionWindow);
       const previousStatus = executionBuilder.status;
-      const shouldEnable = slotsPresent >= faultInspectionWindow - allowedFaults;
+      const shouldEnable = slotsPresent >= Math.min(faultInspectionWindow - allowedFaults, clockSlot);
 
       executionBuilder.updateStatus(shouldEnable);
       // The status changed we should log

packages/beacon-node/test/sim/mergemock.test.ts

@@ -97,11 +97,11 @@ describe("executionEngine / ExecutionEngineHttp", () => {
     const epochsOfMargin = 1;
     const timeoutSetupMargin = 30 * 1000; // Give extra 30 seconds of margin
 
-    // The builder gets activated post middle of epoch because of circuit breaker
-    // In a perfect run expected builder = 16, expected engine = 16
-    //   keeping 4 missed slots margin for both
-    const expectedBuilderBlocks = 12;
-    const expectedEngineBlocks = 12;
+    // We only expect builder blocks since `builderalways` is configured
+    // In a perfect run expected builder = 32, expected engine = 0
+    // keeping 4 missed slots and 4 engine blocks due to fallback as margin
+    const expectedBuilderBlocks = 28;
+    const maximumEngineBlocks = 4;
 
     // All assertions are tracked w.r.t. fee recipient by attaching different fee recipient to
     // execution and builder
@@ -264,9 +264,9 @@ describe("executionEngine / ExecutionEngineHttp", () => {
       throw Error(`Incorrect builderBlocks=${builderBlocks} (expected=${expectedBuilderBlocks})`);
     }
 
-    // 3. engine blocks are as expected
-    if (engineBlocks < expectedEngineBlocks) {
-      throw Error(`Incorrect engineBlocks=${engineBlocks} (expected=${expectedEngineBlocks})`);
+    // 3. engine blocks do not exceed max limit
+    if (engineBlocks > maximumEngineBlocks) {
+      throw Error(`Incorrect engineBlocks=${engineBlocks} (limit=${maximumEngineBlocks})`);
     }
 
     // wait for 1 slot to print current epoch stats