Loki-SCC: Detect driver loop via block dim and use single detection point

[mlange05]

Note: These points arose during the PR review of #150 - please see the PR for more detail.

In the SCC family of single column transformations, we have many mechanisms that influence which loops are regarded as active "driver" loops, and thus need transforming (eg. containment of a "target" call, pragma annotation, etc.). Likewise, several mechanisms depend on this, including de/re-vector processing, as well as pragma annotations.

While we have a single entry-point utility that can determine which loops these are, there are still a set of corner-cases. where additional logic is used to back-out or skip looks previously identified. Changing this will require thorough testing for various regression tests. This issue will track this.