Make code fragments files non-physical with event system disabled

As a side effect it will disable write checks for fragments files

This allows completion work without write action.
Inspired by Java fragment files

compiler/frontend/src/org/jetbrains/kotlin/psi/KtCodeFragment.kt

@@ -53,6 +53,7 @@ abstract class KtCodeFragment(
     private var thisType: PsiType? = null
     private var superType: PsiType? = null
     private var exceptionHandler: JavaCodeFragment.ExceptionHandler? = null
+    private var isPhysical = true
 
     abstract fun getContentElement(): KtElement?
 
@@ -62,7 +63,7 @@ abstract class KtCodeFragment(
 
     override fun getForcedResolveScope() = resolveScope
 
-    override fun isPhysical() = true
+    override fun isPhysical() = isPhysical
 
     override fun isValid() = true
 
@@ -72,9 +73,10 @@ abstract class KtCodeFragment(
 
     override fun clone(): KtCodeFragment {
         val clone = cloneImpl(calcTreeElement().clone() as FileElement) as KtCodeFragment
+        clone.isPhysical = false
         clone.originalFile = this
         clone.imports = imports
-        clone.viewProvider = SingleRootFileViewProvider(PsiManager.getInstance(_project), LightVirtualFile(name, KotlinFileType.INSTANCE, text), true)
+        clone.viewProvider = SingleRootFileViewProvider(PsiManager.getInstance(_project), LightVirtualFile(name, KotlinFileType.INSTANCE, text), false)
         clone.viewProvider.forceCachedPsi(clone)
         return clone
     }