[IR] Simplify usage of IrOverrideUtil

It had some copy-pasted code for counting current file on each use-site.
Now it's encapsulated in strategy.

KT-61934

compiler/ir/serialization.common/src/org/jetbrains/kotlin/backend/common/overrides/FakeOverrides.kt

@@ -86,6 +86,11 @@ private class IrLinkerFakeOverrideBuilderStrategy(
     friendModules = friendModules,
     unimplementedOverridesStrategy = unimplementedOverridesStrategy
 ) {
+
+    override fun inFile(file: IrFile?, block: () -> Unit) {
+        fakeOverrideDeclarationTable.inFile(file, block)
+    }
+
     override fun linkFunctionFakeOverride(function: IrFunctionWithLateBinding, manglerCompatibleMode: Boolean) {
         val (signature, symbol) = computeFunctionFakeOverrideSymbol(function, manglerCompatibleMode)
 
@@ -286,19 +291,11 @@ class IrLinkerFakeOverrideProvider(
 
         if (!platformSpecificClassFilter.needToConstructFakeOverrides(clazz)) return false
 
-        buildFakeOverridesForSingleClass(clazz, compatibilityMode)
+        irOverridingUtil.buildFakeOverridesForClass(clazz, compatibilityMode.oldSignatures)
 
         return true
     }
 
-    fun buildFakeOverridesForSingleClass(clazz: IrClass, compatibilityMode: CompatibilityMode) {
-        fakeOverrideDeclarationTable.run {
-            inFile(clazz.fileOrNull) {
-                irOverridingUtil.buildFakeOverridesForClass(clazz, compatibilityMode.oldSignatures)
-            }
-        }
-    }
-
     fun provideFakeOverrides(klass: IrClass, compatibilityMode: CompatibilityMode) {
         buildFakeOverrideChainsForClass(klass, compatibilityMode)
         haveFakeOverrides.add(klass)