FIR checker: add diagnostic VAR_OVERRIDDEN_BY_VAL

compiler/testData/diagnostics/tests/OverridingVarByVal.fir.kt

@@ -1,15 +0,0 @@
-open class Var() {
-  open var v : Int = 1
-}
-
-interface VarT {
-  var v : Int
-}
-
-class Val() : Var(), VarT {
-  override val v : Int = 1
-}
-
-class Var2() : Var() {
-  override var v : Int = 1
-}

compiler/testData/diagnostics/tests/OverridingVarByVal.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 open class Var() {
   open var v : Int = 1
 }

compiler/testData/diagnostics/tests/annotations/rendering/typeMismatchOnOverride.fir.kt

@@ -17,7 +17,7 @@ interface A {
 interface B : A {
     override val p1: <!PROPERTY_TYPE_MISMATCH_ON_OVERRIDE!>Int<!>
     @An
-    override val p2: @An String
+    override <!VAR_OVERRIDDEN_BY_VAL!>val<!> p2: @An String
     override fun test(arg: String): <!RETURN_TYPE_MISMATCH_ON_OVERRIDE!>Int<!>
 }
 

compiler/testData/diagnostics/tests/regressions/kt3810.fir.kt

@@ -1,5 +0,0 @@
-interface A {
-    var foo: String
-}
-
-class B(override val foo: String) : A

compiler/testData/diagnostics/tests/regressions/kt3810.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 interface A {
     var foo: String
 }

compiler/testData/diagnostics/tests/scopes/kt323.fir.kt

@@ -6,7 +6,7 @@ open class A {
 }
 
 class B : A() {
-    override val a = 34
+    override <!VAR_OVERRIDDEN_BY_VAL!>val<!> a = 34
 
     var b : Int
         public get() = 23