FIR LT: extract syntax diagnostic info from error element

#KT-56701 fixed

analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDataClassConverters.kt

@@ -4931,4 +4931,11 @@ internal val KT_DIAGNOSTIC_CONVERTER = KtDiagnosticConverterBuilder.buildConvert
             token,
         )
     }
+    add(FirSyntaxErrors.SYNTAX_WITH_MESSAGE) { firDiagnostic ->
+        SyntaxWithMessageImpl(
+            firDiagnostic.a,
+            firDiagnostic as KtPsiDiagnostic,
+            token,
+        )
+    }
 }

analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnostics.kt

@@ -3428,4 +3428,9 @@ sealed class KtFirDiagnostic<PSI : PsiElement> : KtDiagnosticWithPsi<PSI> {
         override val diagnosticClass get() = Syntax::class
     }
 
+    abstract class SyntaxWithMessage : KtFirDiagnostic<PsiElement>() {
+        override val diagnosticClass get() = SyntaxWithMessage::class
+        abstract val message: String
+    }
+
 }

analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnosticsImpl.kt

@@ -4150,3 +4150,9 @@ internal class SyntaxImpl(
     override val token: KtLifetimeToken,
 ) : KtFirDiagnostic.Syntax(), KtAbstractFirDiagnostic<PsiElement>
 
+internal class SyntaxWithMessageImpl(
+    override val message: String,
+    override val firDiagnostic: KtPsiDiagnostic,
+    override val token: KtLifetimeToken,
+) : KtFirDiagnostic.SyntaxWithMessage(), KtAbstractFirDiagnostic<PsiElement>
+