[JS IR] suport SuspendN.invoke functions

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/coroutines/AddContinuationToFunctionCallsLowering.kt

@@ -62,9 +62,8 @@ class AddContinuationToFunctionCallsLowering(val context: JsCommonBackendContext
                 }
 
                 val oldFun = expression.symbol.owner
-                val newFun: IrSimpleFunction =
-                    context.mapping.suspendFunctionsToFunctionWithContinuations[oldFun]
-                        ?: error("No mapping for ${oldFun.fqNameWhenAvailable}")
+                // TODO: investigate why mapping might be unavailable for SuspendFunction4.invoke
+                val newFun: IrSimpleFunction = oldFun.getOrCreateFunctionWithContinuationStub(context)
 
                 return irCall(
                     expression,

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/coroutines/AddContinuationToFunctionsLowering.kt

@@ -85,7 +85,7 @@ private fun transformSuspendFunction(context: JsCommonBackendContext, function:
 }
 
 
-private fun IrSimpleFunction.getOrCreateFunctionWithContinuationStub(context: JsCommonBackendContext): IrSimpleFunction {
+fun IrSimpleFunction.getOrCreateFunctionWithContinuationStub(context: JsCommonBackendContext): IrSimpleFunction {
     return context.mapping.suspendFunctionsToFunctionWithContinuations.getOrPut(this) {
         createSuspendFunctionStub(context)
     }