[FIR JS] Create an LT diagnostics with BE runner

js/js.tests/test/org/jetbrains/kotlin/generators/tests/GenerateJsTests.kt

@@ -238,6 +238,15 @@ fun main(args: Array<String>) {
                 )
             }
 
+            testClass<AbstractFirLightTreeJsDiagnosticWithBackendTest>(suiteTestClassName = "FirLightTreeJsOldFrontendDiagnosticsWithBackendTestGenerated") {
+                model(
+                    relativeRootPath = "diagnostics/testsWithJsStdLibAndBackendCompilation",
+                    pattern = "^([^_](.+))\\.kt$",
+                    excludedPattern = excludedFirTestdataPattern,
+                    targetBackend = TargetBackend.JS_IR
+                )
+            }
+
             testClass<AbstractDiagnosticsTestWithJsStdLib>(suiteTestClassName = "DiagnosticsWithJsStdLibTestGenerated") {
                 model(
                     relativeRootPath = "diagnostics/testsWithJsStdLib",

js/js.tests/test/org/jetbrains/kotlin/js/test/fir/AbstractFirPsiJsDiagnosticTest.kt

@@ -104,3 +104,4 @@ abstract class AbstractFirPsiJsDiagnosticTest : AbstractFirJsDiagnosticTestBase(
 abstract class AbstractFirLightTreeJsDiagnosticTest : AbstractFirJsDiagnosticTestBase(FirParser.LightTree)
 
 abstract class AbstractFirPsiJsDiagnosticWithBackendTest : AbstractFirJsDiagnosticWithBackendTestBase(FirParser.Psi)
+abstract class AbstractFirLightTreeJsDiagnosticWithBackendTest : AbstractFirJsDiagnosticWithBackendTestBase(FirParser.LightTree)