[FIR] Add EXPECT_ACTUAL_MODIFIER positioning strategy

compiler/frontend.common-psi/src/org/jetbrains/kotlin/diagnostics/LightTreePositioningStrategies.kt

@@ -458,6 +458,9 @@ object LightTreePositioningStrategies {
     val EXTERNAL_MODIFIER: LightTreePositioningStrategy =
         ModifierSetBasedLightTreePositioningStrategy(KtTokens.EXTERNAL_KEYWORD)
 
+    val EXPECT_ACTUAL_MODIFIER: LightTreePositioningStrategy =
+        ModifierSetBasedLightTreePositioningStrategy(KtTokens.EXPECT_KEYWORD, KtTokens.ACTUAL_KEYWORD)
+
     val OBJECT_KEYWORD: LightTreePositioningStrategy = keywordStrategy { objectKeyword(it) }
 
     val FIELD_KEYWORD: LightTreePositioningStrategy = keywordStrategy { fieldKeyword(it) }

compiler/frontend.common-psi/src/org/jetbrains/kotlin/diagnostics/PositioningStrategies.kt

@@ -313,6 +313,10 @@ object PositioningStrategies {
     val EXTERNAL_MODIFIER: PositioningStrategy<KtModifierListOwner> =
         ModifierSetBasedPositioningStrategy(KtTokens.EXTERNAL_KEYWORD)
 
+    @JvmField
+    val EXPECT_ACTUAL_MODIFIER: PositioningStrategy<KtModifierListOwner> =
+        ModifierSetBasedPositioningStrategy(KtTokens.EXPECT_KEYWORD, KtTokens.ACTUAL_KEYWORD)
+
     @JvmField
     val OBJECT_KEYWORD: PositioningStrategy<KtObjectDeclaration> = object : PositioningStrategy<KtObjectDeclaration>() {
         override fun mark(element: KtObjectDeclaration): List<TextRange> {

compiler/frontend.common-psi/src/org/jetbrains/kotlin/diagnostics/SourceElementPositioningStrategies.kt

@@ -123,6 +123,11 @@ object SourceElementPositioningStrategies {
         PositioningStrategies.DATA_MODIFIER
     )
 
+    val EXPECT_ACTUAL_MODIFIER = SourceElementPositioningStrategy(
+        LightTreePositioningStrategies.EXPECT_ACTUAL_MODIFIER,
+        PositioningStrategies.EXPECT_ACTUAL_MODIFIER
+    )
+
     val OBJECT_KEYWORD = SourceElementPositioningStrategy(
         LightTreePositioningStrategies.OBJECT_KEYWORD,
         PositioningStrategies.OBJECT_KEYWORD