"field": backing field usage deprecated warning, relevant diagnostics tests changed

compiler/testData/diagnostics/tests/backingField/ReadForwardInAnonymous.kt

@@ -1,6 +1,6 @@
 class ReadForward() {
     init {
-        val <!UNUSED_VARIABLE!>x<!> = <!UNINITIALIZED_VARIABLE!>$a<!>
+        val <!UNUSED_VARIABLE!>x<!> = <!BACKING_FIELD_USAGE_DEPRECATED, UNINITIALIZED_VARIABLE!>$a<!>
     }
 
     val a = 1

compiler/testData/diagnostics/tests/backingField/ReadForwardInPropertyInitializer.kt

@@ -1,4 +1,4 @@
 class ReadForward() {
-    val a = <!UNINITIALIZED_VARIABLE!>$b<!>
+    val a = <!BACKING_FIELD_USAGE_DEPRECATED, UNINITIALIZED_VARIABLE!>$b<!>
     val b = 1
 }

compiler/testData/diagnostics/tests/backingField/ReadInAnonymous.kt

@@ -1,6 +1,6 @@
 class ReadByAnotherPropertyInitializer() {
     val a = 1
     init {
-        val <!UNUSED_VARIABLE!>x<!> = $a
+        val <!UNUSED_VARIABLE!>x<!> = <!BACKING_FIELD_USAGE_DEPRECATED!>$a<!>
     }
 }

compiler/testData/diagnostics/tests/backingField/ReadInAnotherPropertyIntializer.kt

@@ -1,4 +1,4 @@
 class ReadByAnotherPropertyInitializer() {
     val a = 1
-    val b = $a
+    val b = <!BACKING_FIELD_USAGE_DEPRECATED!>$a<!>
 }

compiler/testData/diagnostics/tests/backingField/ReadInFunction.kt

@@ -1,4 +1,4 @@
 class ReadByAnotherPropertyInitializer() {
     val a = 1
-    fun ff() = $a
+    fun ff() = <!BACKING_FIELD_USAGE_DEPRECATED!>$a<!>
 }

compiler/testData/diagnostics/tests/backingField/kt462BackingFieldsResolve.kt

@@ -49,7 +49,7 @@ abstract class TestInitializationWithoutBackingField() {
 abstract class TestInitializationThroughBackingField() {
     val valWithBackingField : Int
     init {
-        $valWithBackingField = 2
+        <!BACKING_FIELD_USAGE_DEPRECATED!>$valWithBackingField<!> = 2
     }
 
     val valWithoutBackingField : Int
@@ -60,12 +60,12 @@ abstract class TestInitializationThroughBackingField() {
 
     var finalDefaultVar : Int
     init {
-        $finalDefaultVar = 3
+        <!BACKING_FIELD_USAGE_DEPRECATED!>$finalDefaultVar<!> = 3
     }
 
     open var openVar : Int
     init {
-        $openVar = 4
+        <!BACKING_FIELD_USAGE_DEPRECATED!>$openVar<!> = 4
     }
 
     var varWithCustomSetter : Int
@@ -73,7 +73,7 @@ abstract class TestInitializationThroughBackingField() {
         field = v
     }
     init {
-        $varWithCustomSetter = 3
+        <!BACKING_FIELD_USAGE_DEPRECATED!>$varWithCustomSetter<!> = 3
     }
 
     var varWithoutBackingField : Int
@@ -92,12 +92,12 @@ abstract class TestInitializationThroughBackingField() {
 class TestBackingFieldsVisibility() {
     var a : Int = 712
     init {
-        $a = 37
+        <!BACKING_FIELD_USAGE_DEPRECATED!>$a<!> = 37
         this.$a = 357
     }
 
     fun foo() {
-        $a = 334
+        <!BACKING_FIELD_USAGE_DEPRECATED!>$a<!> = 334
         this.$a = 347
     }
 
@@ -110,7 +110,7 @@ class TestBackingFieldsVisibility() {
     val x = <!INACCESSIBLE_BACKING_FIELD!>$topLevelVar<!>
 
     inner class Inner() {
-        val z = this@TestBackingFieldsVisibility.$x
+        val z = this@TestBackingFieldsVisibility.<!BACKING_FIELD_USAGE_DEPRECATED!>$x<!>
     }
 
     <!ABSTRACT_PROPERTY_IN_NON_ABSTRACT_CLASS!>abstract<!> val w = 11
@@ -150,7 +150,7 @@ class T() {
         return 1
     }
 
-    var r: Int = $x
+    var r: Int = <!BACKING_FIELD_USAGE_DEPRECATED!>$x<!>
     set(v: Int) {
         if (true) {
             field = 33
@@ -161,11 +161,11 @@ class T() {
     }
 
     fun bar() {
-        $x = 34
+        <!BACKING_FIELD_USAGE_DEPRECATED!>$x<!> = 34
         val <!UNUSED_VARIABLE!>o<!> = object {
-            val y = $x
+            val y = <!BACKING_FIELD_USAGE_DEPRECATED!>$x<!>
             init {
-                $x = 422
+                <!BACKING_FIELD_USAGE_DEPRECATED!>$x<!> = 422
             }
         }
     }