Add variance (in / out) modifier inspection #KT-11090 Fixed

idea/testData/inspections/addVarianceModifier/test.kt

@@ -0,0 +1,24 @@
+interface EffectivelyOut<T> {
+    fun foo(): T
+    val bar: T
+}
+interface EffectivelyIn<T> {
+    fun foo(arg: T)
+}
+interface Invariant1<T> {
+    var bar: T
+}
+interface Invariant2<T> {
+    fun T.foo(): T
+}
+interface Invariant3<T : Invariant1<T>> {
+    fun T.foo()
+}
+abstract class AbstractOut<T> {
+    abstract val foo: T
+    private var bar = foo
+}
+abstract class AbstractIn<T>(private val foo: T) {
+    fun bar(arg: T) = foo == arg
+}
+interface Empty<T>