[debugger] Thread Dump fixes

* explicitly show in UI when some dump items weren't collected
* fix duplicated platform threads (in case of any timeouts/errors)
* fix data-race during waiting for evaluatable context

GitOrigin-RevId: e8f75a53a67bba331dd0e713ec3857bb1604dd29

java/java-frontback-impl/src/com/intellij/unscramble/DumpItem.kt

@@ -245,3 +245,31 @@ private class JavaThreadDumpItem(private val threadState: ThreadState) : Mergeab
   }
 }
 
+class InfoDumpItem(private val title: @Nls String, private val details: @NlsSafe String) : MergeableDumpItem {
+  override val mergeableToken: MergeableToken = object : MergeableToken {
+    override fun equals(other: Any?) = super.equals(other)
+    override fun hashCode() = super.hashCode()
+    override val item = this@InfoDumpItem
+  }
+
+  override val name: @NlsSafe String
+    get() = title
+  override val stateDesc: @NlsSafe String
+    get() = ""
+  override val stackTrace: @NlsSafe String
+    get() = details
+  override val interestLevel: Int
+    get() = Int.MIN_VALUE
+  override val icon: Icon
+    get() = AllIcons.General.Information
+  override val iconToolTip: @Nls String?
+    get() = null
+  override val attributes: SimpleTextAttributes
+    get() = SimpleTextAttributes.REGULAR_ATTRIBUTES
+  override val isDeadLocked: Boolean
+    get() = false
+  override val awaitingDumpItems: Set<DumpItem>
+    get() = emptySet()
+
+}
+