Implemented collecting use-old-backend flag from Gradle

#KT-46689 Fixed

idea/idea-gradle/src/org/jetbrains/kotlin/idea/statistics/KotlinGradleFUSLogger.kt

@@ -129,7 +129,8 @@ class KotlinGradleFUSLogger : StartupActivity, DumbAware, Runnable {
                 BooleanMetrics.ENABLED_COMPILER_PLUGIN_JPA_SUPPORT,
                 BooleanMetrics.ENABLED_COMPILER_PLUGIN_SAM_WITH_RECEIVER,
                 BooleanMetrics.JVM_COMPILER_IR_MODE,
-                StringMetrics.JVM_DEFAULTS
+                StringMetrics.JVM_DEFAULTS,
+                StringMetrics.USE_OLD_BACKEND
             )
 
             container.log(

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

@@ -134,10 +134,13 @@ internal open class GradleCompilerRunner(
         // compiler would report metrics by itself via JMX
         KotlinBuildStatsService.applyIfInitialised {
             if (compilerArgs is K2JVMCompilerArguments) {
-                val args = K2JVMCompilerArguments()
-                parseCommandLineArguments(argsArray.toList(), args)
-                KotlinBuildStatsService.getInstance()?.report(BooleanMetrics.JVM_COMPILER_IR_MODE, args.useIR)
-                KotlinBuildStatsService.getInstance()?.report(StringMetrics.JVM_DEFAULTS, args.jvmDefault)
+                KotlinBuildStatsService.getInstance()?.apply {
+                    val args = K2JVMCompilerArguments()
+                    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())
+                }
             }
         }
 

libraries/tools/kotlin-gradle-statistics/src/org/jetbrains/kotlin/statistics/metrics/StringMetrics.kt

@@ -46,4 +46,6 @@ enum class StringMetrics(val type: StringOverridePolicy, val anonymization: Stri
 
     // Compiler parameters
     JVM_DEFAULTS(CONCAT, SAFE),
+    USE_OLD_BACKEND(CONCAT, SAFE)
+
 }