C2: Cleanup loop invariance handling for data nodes dependent on projection into the loop

JDK-8146792 added code to treat data nodes which are dependent on the projection into the loop (after all predicates) as non-loop invariant. This avoids that a predicate is created with nodes that are still pinned further down at the projection into a loop (leads to a broken graph). A follow-up fix was required to fix some edge cases not covered by JDK-8146792 (JDK-8277529). However, the entire special handling for such data nodes should be revisited: We should directly compute the invariance based on other nodes and not preset them as non-invariant in the constructor. This makes it less error-prone and avoids surprises in the future when other new nodes are created which did not get the special check in the constructor.