Report deprecation warning when -Xuse-old-backend is specified

#KT-48532

compiler/cli/src/org/jetbrains/kotlin/cli/jvm/jvmArguments.kt

@@ -212,13 +212,20 @@ fun CompilerConfiguration.configureAdvancedJvmOptions(arguments: K2JVMCompilerAr
                 arguments.useIR && !useOldBackend
             }
 
-    if (arguments.useIR && arguments.useOldBackend) {
+    if (arguments.useOldBackend) {
         messageCollector.report(
             STRONG_WARNING,
-            "Both -Xuse-ir and -Xuse-old-backend are passed. This is an inconsistent configuration. " +
-                    "The compiler will use the ${if (useIR) "JVM IR" else "old JVM"} backend"
+            "-Xuse-old-backend is deprecated and will be removed in a future release"
         )
+        if (arguments.useIR) {
+            messageCollector.report(
+                STRONG_WARNING,
+                "Both -Xuse-ir and -Xuse-old-backend are passed. This is an inconsistent configuration. " +
+                        "The compiler will use the ${if (useIR) "JVM IR" else "old JVM"} backend"
+            )
+        }
     }
+
     messageCollector.report(LOGGING, "Using ${if (useIR) "JVM IR" else "old JVM"} backend")
 
     put(JVMConfigurationKeys.IR, useIR)

compiler/testData/cli/jvm/abiStabilityUnstableWithOldBackend.out

@@ -1,2 +1,3 @@
+warning: -Xuse-old-backend is deprecated and will be removed in a future release
 error: -Xabi-stability=unstable is not supported in the old JVM backend
 COMPILATION_ERROR

compiler/testData/cli/jvm/bothJvmIrAndOldBackend.out

@@ -1,2 +1,3 @@
+warning: -Xuse-old-backend is deprecated and will be removed in a future release
 warning: both -Xuse-ir and -Xuse-old-backend are passed. This is an inconsistent configuration. The compiler will use the old JVM backend
 OK

compiler/testData/cli/jvm/classAndTraitClash.out

@@ -1,3 +1,4 @@
+warning: -Xuse-old-backend is deprecated and will be removed in a future release
 compiler/testData/cli/jvm/classAndTraitClash.kt:3:1: error: duplicate JVM class name 'test/T1$DefaultImpls' generated from: `T1$DefaultImpls`, T1
 interface  T1 {
 ^

compiler/testData/cli/jvm/suspendInFunInterfaceIrDisabled.out

@@ -1,3 +1,4 @@
+warning: -Xuse-old-backend is deprecated and will be removed in a future release
 compiler/testData/cli/jvm/suspendInFunInterfaceIrDisabled.kt:2:5: error: 'suspend' modifier is not allowed on a single abstract member
     suspend fun foo()
     ^