[LL API] Refactor session caches

Use 'CachedValue' and dependency handling with 'ModificationTracker'
for dependent session invalidation.

analysis/analysis-internal-utils/src/org/jetbrains/kotlin/analysis/utils/trackers/CompositeModificationTracker.kt

@@ -6,15 +6,39 @@
 package org.jetbrains.kotlin.analysis.utils.trackers
 
 import com.intellij.openapi.util.ModificationTracker
+import java.util.*
+import kotlin.collections.ArrayList
 
 public class CompositeModificationTracker private constructor(private val trackers: List<ModificationTracker>) : ModificationTracker {
     override fun getModificationCount(): Long = trackers.sumOf { it.modificationCount }
 
     public companion object {
-        public fun create(trackers: List<ModificationTracker>): ModificationTracker = when (trackers.size) {
-            0 -> ModificationTracker.NEVER_CHANGED
-            1 -> trackers.single()
-            else -> CompositeModificationTracker(trackers)
+        public fun create(trackers: List<ModificationTracker>): ModificationTracker {
+            return when (trackers.size) {
+                0 -> ModificationTracker.NEVER_CHANGED
+                1 -> trackers.single()
+                else -> CompositeModificationTracker(trackers)
+            }
+        }
+
+        public fun createFlattened(trackers: List<ModificationTracker>): ModificationTracker {
+            val map = IdentityHashMap<ModificationTracker, Boolean>()
+            val flattened = ArrayList<ModificationTracker>()
+
+            fun flatten(tracker: ModificationTracker) {
+                when (tracker) {
+                    is CompositeModificationTracker -> tracker.trackers.forEach(::flatten)
+                    ModificationTracker.NEVER_CHANGED -> {}
+                    else -> {
+                        if (map.put(tracker, true) == null) {
+                            flattened += tracker
+                        }
+                    }
+                }
+            }
+
+            trackers.forEach(::flatten)
+            return create(flattened)
         }
     }
 }