[LL API] Refactoring, make 'timestamp' a member

analysis/low-level-api-fir/src/org/jetbrains/kotlin/analysis/low/level/api/fir/file/structure/FileStructure.kt

@@ -194,8 +194,7 @@ internal class FileStructure private constructor(
             val firCodeFragment = firFile.codeFragment
             firCodeFragment.lazyResolveToPhase(FirResolvePhase.BODY_RESOLVE)
 
-            val timestamp = container.modificationStamp
-            ReanalyzableCodeFragmentStructureElement(firFile, container, firCodeFragment.symbol, timestamp, moduleComponents)
+            ReanalyzableCodeFragmentStructureElement(firFile, container, firCodeFragment.symbol, moduleComponents)
         }
         container is KtFile -> {
             val firFile = moduleComponents.firFileBuilder.buildRawFirFileWithCaching(ktFile)

analysis/low-level-api-fir/src/org/jetbrains/kotlin/analysis/low/level/api/fir/file/structure/FileStructureElement.kt

@@ -141,10 +141,10 @@ internal class ReanalyzableCodeFragmentStructureElement(
     firFile: FirFile,
     override val psi: KtCodeFragment,
     firSymbol: FirCodeFragmentSymbol,
-    override val timestamp: Long,
     moduleComponents: LLFirModuleResolveComponents,
 ) : ReanalyzableStructureElement<KtCodeFragment, FirCodeFragmentSymbol>(firFile, firSymbol, moduleComponents) {
     override val mappings = KtToFirMapping(firSymbol.fir, recorder)
+    override val timestamp = psi.modificationStamp
 
     override fun reanalyze(): ReanalyzableStructureElement<KtCodeFragment, FirCodeFragmentSymbol> {
         val originalCodeFragment = firSymbol.fir
@@ -166,13 +166,7 @@ internal class ReanalyzableCodeFragmentStructureElement(
         val newCodeFragment = firFile.codeFragment
         newCodeFragment.lazyResolveToPhase(FirResolvePhase.BODY_RESOLVE)
 
-        return ReanalyzableCodeFragmentStructureElement(
-            firFile,
-            psi,
-            newCodeFragment.symbol,
-            psi.modificationStamp,
-            moduleComponents
-        )
+        return ReanalyzableCodeFragmentStructureElement(firFile, psi, newCodeFragment.symbol, moduleComponents)
     }
 }