[PSI] KtCommonFile: optimize search for importList

There is no need to search for more than one list

^KT-73687

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

@@ -1,17 +1,6 @@
 /*
- * Copyright 2010-2015 JetBrains s.r.o.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
+ * Copyright 2010-2024 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
 package org.jetbrains.kotlin.psi
@@ -29,6 +18,7 @@ import com.intellij.psi.tree.IElementType
 import com.intellij.testFramework.LightVirtualFile
 import com.intellij.util.messages.Topic
 import org.jetbrains.kotlin.idea.KotlinFileType
+import org.jetbrains.kotlin.psi.KtCodeFragment.Companion.IMPORT_SEPARATOR
 import org.jetbrains.kotlin.psi.psiUtil.getElementTextWithContext
 
 abstract class KtCodeFragment(
@@ -198,6 +188,9 @@ abstract class KtCodeFragment(
         return null
     }
 
+    override val importList: KtImportList?
+        get() = importsAsImportList()
+
     override val importLists: List<KtImportList>
         get() = listOfNotNull(importsAsImportList())
 

compiler/psi/src/org/jetbrains/kotlin/psi/KtCommonFile.kt

@@ -51,8 +51,8 @@ open class KtCommonFile(viewProvider: FileViewProvider, val isCompiled: Boolean)
     @Volatile
     private var pathCached: String? = null
 
-    val importList: KtImportList?
-        get() = importLists.firstOrNull()
+    open val importList: KtImportList?
+        get() = findChildByTypeOrClass(KtStubElementTypes.IMPORT_LIST, KtImportList::class.java)
 
     @Volatile
     private var hasImportAlias: Boolean? = null