Add "skipped" navigation state to DAST

Recently with DAST v6.20.0, the Grouped URLs configuration was released (Group URLs configuration for DAST (#555583 - closed) • Arpit Gogia • 18.5) to allow customers to reduce crawl time by skipping similar URLs.

When a page is skipped by the crawler because of matching a grouped URL pattern, the current implementation options to indicate this in the crawl graph are: (1) show in the "visited" section (2) show in the "failed" section.

Neither of these options indicate that the page was intentionally skipped because of matching a grouped URL pattern.

I am proposing the introduction of a new state "Skipped" in the crawl graph to communicate this explicitly.

This state should be distinctly identified in the logs and in the crawl graph.

Note: Navigations excluded by SCOPE also show up as failures.