Exclude the HeapTaskDaemon from blocked thread warnings.

It's just how the thing works in a lot of cases, and it's polluting the
logs with instances of nothing but several blocked HeapTaskDaemons.

core-util/src/main/java/org/signal/core/util/concurrent/DeadlockDetector.kt

@@ -27,12 +27,15 @@ class DeadlockDetector(private val handler: Handler, private val pollingInterval
 
   private fun poll() {
     val threads: Map<Thread, Array<StackTraceElement>> = Thread.getAllStackTraces()
-    val blocked: Map<Thread, Array<StackTraceElement>> = threads.filter { entry ->
+    val blocked: Map<Thread, Array<StackTraceElement>> = threads
+      .filter { entry ->
         val thread: Thread = entry.key
         val stack: Array<StackTraceElement> = entry.value
 
         thread.state == Thread.State.BLOCKED || (thread.state == Thread.State.WAITING && stack.any { it.methodName.startsWith("lock") })
       }
+      .filter { entry -> !BLOCK_BLACKLIST.contains(entry.key.name) }
+
     val blockedIds: Set<Long> = blocked.keys.map(Thread::getId).toSet()
     val stillBlocked: Set<Long> = blockedIds.intersect(previouslyBlocked)
 
@@ -93,6 +96,8 @@ class DeadlockDetector(private val handler: Handler, private val pollingInterval
 
     private const val CONCERNING_QUEUE_THRESHOLD = 4
 
+    private val BLOCK_BLACKLIST = setOf("HeapTaskDaemon")
+
     private fun buildLogString(description: String, blocked: Map<Thread, Array<StackTraceElement>>): String {
       val stringBuilder = StringBuilder()
       stringBuilder.append(description).append("\n")