Jvm-abi-gen: do not treat KmProperty.hasConstant as part of ABI

... for non-const properties.

The meaning of this flag for non-const properties is in reality not
well-established, and it can vary from one release to another. In
particular, it's different in K2.

This commit has two parts:
1) The test (added in 5891617674) about clinit is changed. Original
   motivation was to check that presence or absence of `<clinit>` is not
   a part of the ABI. However, in addition to that, the test also
   involuntarily checked that the aforementioned "hasConstant" flag for
   the property y/Object.y is the same in both cases (which I believe
   was not the intention) because these tests check that Kotlin metadata
   is _exactly the same_ after applying jvm-abi-gen. So I've changed it
   to be more straightforward: one version declares an obvious constant,
   while another declares an obvious non-constant. After this change,
   the test started to fail (even on K1) because the value of the
   "hasConstant" flag was different between two versions.
2) Remove "hasConstant" flag for non-const properties when transforming
   metadata via jvm-abi-gen. This fixes the test and assures it won't
   fail when the project is migrated to LV 2.0.

 #KT-60849 Fixed

plugins/jvm-abi-gen/testData/compare/clinit/base/Object.kt

@@ -2,5 +2,4 @@ package test
 
 object Object {
     val x = 0
-    val y = x
-}
+}