Move lateinit assertion for companion property to companion object

Previously, for a property named `x` in the companion object of a class
named `Foo`, we generated:
- `Foo.access$getX$cp`, consisting of `GETFIELD Foo.x` and lateinit
  assertion
- `Foo.Companion.getX`, consisting of `INVOKEVIRTUAL Foo.access$getX$cp`

Now, we generate:
- `Foo.access$getX$cp`, consisting of `GETFIELD Foo.x`
- `Foo.Companion.getX`, consisting of `INVOKEVIRTUAL Foo.access$getX$cp`
  and lateinit assertion

The reason is that this way we can avoid generating another accessor and
reuse `Foo.access$getX$cp` in case `isInitialized` is called on a
lateinit property from companion.

For private properties, getX is not generated, but instead the assertion
is generated on each access to the field (which can be improved, see
KT-28331). The same happens for access to non-private properties from
inside the same context where they're declared.

 #KT-21862 In Progress

compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java

@@ -17794,6 +17794,11 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
                 runTest("compiler/testData/codegen/box/properties/lateinit/accessorException.kt");
             }
 
+            @TestMetadata("accessorExceptionPublic.kt")
+            public void testAccessorExceptionPublic() throws Exception {
+                runTest("compiler/testData/codegen/box/properties/lateinit/accessorExceptionPublic.kt");
+            }
+
             public void testAllFilesPresentInLateinit() throws Exception {
                 KotlinTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("compiler/testData/codegen/box/properties/lateinit"), Pattern.compile("^(.+)\\.kt$"), TargetBackend.JVM, true);
             }