Report error on -Xuse-old-backend, remove Gradle option useOldBackend

Allow using old JVM backend only to compile kts.

 #KT-48532 Fixed

libraries/tools/kotlin-gradle-plugin-api/src/common/kotlin/org/jetbrains/kotlin/gradle/dsl/KotlinJvmOptions.kt

@@ -29,10 +29,4 @@ interface KotlinJvmOptions  : org.jetbrains.kotlin.gradle.dsl.KotlinCommonOption
      * Default value: false
      */
      var noJdk: kotlin.Boolean
-
-    /**
-     * Use the old JVM backend
-     * Default value: false
-     */
-     var useOldBackend: kotlin.Boolean
 }

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/compilerRunner/GradleKotlinCompilerRunner.kt

@@ -151,7 +151,6 @@ internal open class GradleCompilerRunner(
                         parseCommandLineArguments(argsArray.toList(), args)
                         report(BooleanMetrics.JVM_COMPILER_IR_MODE, args.useIR)
                         report(StringMetrics.JVM_DEFAULTS, args.jvmDefault)
-                        report(StringMetrics.USE_OLD_BACKEND, args.useOldBackend.toString())
                         report(StringMetrics.USE_FIR, args.useK2.toString())
 
                         val pluginPatterns = listOf(Pair(BooleanMetrics.ENABLED_COMPILER_PLUGIN_ALL_OPEN, "kotlin-allopen-.*jar"),

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/dsl/KotlinJvmOptionsBase.kt

@@ -55,13 +55,6 @@ internal abstract class KotlinJvmOptionsBase : org.jetbrains.kotlin.gradle.dsl.K
             noJdkField = value
         }
 
-    private var useOldBackendField: kotlin.Boolean? = null
-    override var useOldBackend: kotlin.Boolean
-        get() = useOldBackendField ?: false
-        set(value) {
-            useOldBackendField = value
-        }
-
     internal open fun updateArguments(args: org.jetbrains.kotlin.cli.common.arguments.K2JVMCompilerArguments) {
         allWarningsAsErrorsField?.let { args.allWarningsAsErrors = it }
         suppressWarningsField?.let { args.suppressWarnings = it }
@@ -73,7 +66,6 @@ internal abstract class KotlinJvmOptionsBase : org.jetbrains.kotlin.gradle.dsl.K
         jvmTarget?.let { args.jvmTarget = it }
         moduleName?.let { args.moduleName = it }
         noJdkField?.let { args.noJdk = it }
-        useOldBackendField?.let { args.useOldBackend = it }
     }
 }
 
@@ -88,7 +80,6 @@ internal fun org.jetbrains.kotlin.cli.common.arguments.K2JVMCompilerArguments.fi
     jvmTarget = null
     moduleName = null
     noJdk = false
-    useOldBackend = false
     noStdlib = true
     noReflect = true
 }