JVM IR: rename private fields for properties with same name

This is needed to get rid of the code that appends "$companion" to
properties moved from companion, because it caused inconsistencies in
the ABI and in JVM signatures stored in the metadata

compiler/testData/codegen/box/fieldRename/jvmFieldNoClash2.kt

@@ -0,0 +1,23 @@
+// TARGET_BACKEND: JVM
+// WITH_RUNTIME
+
+class A {
+    val x = "outer"
+    val y = "outer"
+
+    companion object {
+        @JvmField
+        val x = "companion"
+
+        const val y = "companion"
+    }
+}
+
+fun box(): String {
+    if (A().x != "outer") return "Fail outer x"
+    if (A().y != "outer") return "Fail outer y"
+    if (A.x != "companion") return "Fail companion x"
+    if (A.y != "companion") return "Fail companion y"
+
+    return "OK"
+}