Do join weakRefCleanerThread in DebugProbes.uninstall

Otherwise, multiple pairs of install + uninstall may leave multiple cleanup threads in the state when the map is already cleaned up, but its size is not

Fixes #3028

Author: qwwdfsad

kotlinx-coroutines-core/jvm/src/debug/internal/ConcurrentWeakMap.kt

@@ -73,7 +73,7 @@ internal class ConcurrentWeakMap<K : Any, V: Any>(
             while (true) {
                 cleanWeakRef(weakRefQueue.remove() as HashedWeakRef<*>)
             }
-        } catch(e: InterruptedException) {
+        } catch (e: InterruptedException) {
             Thread.currentThread().interrupt()
         }
     }

kotlinx-coroutines-core/jvm/src/debug/internal/DebugProbesImpl.kt

@@ -102,8 +102,10 @@ internal object DebugProbesImpl {
     }
 
     private fun stopWeakRefCleanerThread() {
-        weakRefCleanerThread?.interrupt()
+        val thread = weakRefCleanerThread ?: return
         weakRefCleanerThread = null
+        thread.interrupt()
+        thread.join()
     }
 
     public fun hierarchyToString(job: Job): String = coroutineStateLock.write {