Use file.modificationStamp to invalidate caches for synthetic files

It previously worked because of updating all counters. That behaviour was removed in
https://github.com/JetBrains/intellij-community/commit/3b860d69ee1b32b210ddf88b1e042dd70ea87cd9.

getUserData(FILE_OUT_OF_BLOCK_MODIFICATION_COUNT) is probably useless because copied file has
isEventSystemEnabled() == false that prevents sending notifications about PSI changes. This need additional checks.

idea/idea-analysis/src/org/jetbrains/kotlin/idea/caches/resolve/KotlinCacheServiceImpl.kt

@@ -137,7 +137,8 @@ class KotlinCacheServiceImpl(val project: Project) : KotlinCacheService {
         val syntheticFileModule = files.map { it.getModuleInfo() }.toSet().single()
         val sdk = syntheticFileModule.sdk
         val filesModificationTracker = ModificationTracker {
-            files.sumByLong { it.outOfBlockModificationCount }
+            // TODO: Check getUserData(FILE_OUT_OF_BLOCK_MODIFICATION_COUNT) actually works
+            files.sumByLong { it.outOfBlockModificationCount + it.modificationStamp }
         }
         val dependenciesForSyntheticFileCache = listOf(PsiModificationTracker.OUT_OF_CODE_BLOCK_MODIFICATION_COUNT, filesModificationTracker)
         val debugName = "completion/highlighting in $syntheticFileModule for files ${files.joinToString { it.name }} for platform $targetPlatform"