Add params (MaxDepth and StopOnSysAdmin) and perf increases to Get-SQLServerLinkCrawl

[MJVL]

This PR adds the following enhancements to Get-SQLServerLinkCrawl:

• Performance increase
  • Crawling will no longer re-visit traversed links (same server with the same user)
  • This avoids circular dependencies, and cut down runtimes from days to a single hour in test environments with tens of servers, hundreds of links, and many circular links
  • Cuts down on noise and query amounts significantly
• MaxDepth param
  • Allows for a max depth of the crawl, which can help to early exit in large environments
• StopOnSysAdmin param
  • Stop crawl upon finding the first SysAdmin link

[v-p-b]

Great additions! Resolving circular dependencies is very important, as infinite loops can take cause performance issues on target systems.

[nullbind]

Im sorry it took me so long to see this. I'll try to review your updates in the next few weeks. Superficially they look great.
Thank you for taking the time to submit the features/fixes!

[MJVL]

Im sorry it took me so long to see this. I'll try to review your updates in the next few weeks. Superficially they look great. Thank you for taking the time to submit the features/fixes!

Coming back to this after forgetting about it for a while. Is this still good to review/merge?

[v-p-b]

As an excuse to ping this thread let me mention that without this PR running PowerUpSQL on a real infra represented by the link network graph in the blog post linked from the wiki will likely DoS all servers except the 2014 :)