[test] Move irText tests from fir2ir/testData to compiler/testData

Let's store them conveniently in one place!

compiler/testData/ir/irText/properties/backingField/backingFieldVisibility.kt

@@ -0,0 +1,21 @@
+// FIR_IDENTICAL
+
+class A {
+    val a: Number
+        private field = 1
+
+    val b: Number
+        internal field = a + 2
+
+    val c = 1
+    val d = c + 2
+
+    fun rest() {
+        val aI = A().a + 10
+        val bI = A().b + 20
+    }
+}
+
+fun test() {
+    val bA = A().b + 20
+}