Never put pooled connections in the result queue (#7154)

In a race this could cause us to prefer a new connection over
a pooled connection, which violates our invariant that pooled
connections are always used if they're found.

Closes: https://github.com/square/okhttp/issues/7152

okhttp-testing-support/src/main/kotlin/okhttp3/internal/concurrent/TaskFaker.kt

@@ -15,6 +15,8 @@
  */
 package okhttp3.internal.concurrent
 
+import okhttp3.OkHttpClient
+import org.assertj.core.api.Assertions.assertThat
 import java.io.Closeable
 import java.util.AbstractQueue
 import java.util.concurrent.BlockingQueue
@@ -23,8 +25,6 @@ import java.util.concurrent.Semaphore
 import java.util.concurrent.TimeUnit
 import java.util.concurrent.atomic.AtomicBoolean
 import java.util.logging.Logger
-import okhttp3.OkHttpClient
-import org.assertj.core.api.Assertions.assertThat
 
 /**
  * Runs a [TaskRunner] in a controlled environment so that everything is sequential and
@@ -266,6 +266,14 @@ class TaskFaker : Closeable {
     }
   }
 
+  /**
+   * Artificially stall until manually resumed by the test thread with [runTasks]. Use this to
+   * simulate races in tasks that doesn't have a deterministic sequence.
+   */
+  fun yield() {
+    stall()
+  }
+
   /**
    * This blocking queue hooks into a fake clock rather than using regular JVM timing for functions
    * like [poll]. It is only usable within task faker tasks.