Adds [Guid] , [String], and [NonTraversingPath] annotation attributes to help with validating HTTP and configuration inputs, along with tests for each. Previously [AbsolutePath] and [RelativePath] were testing for traversal segments, and that logic has been taken out; all paths require an explicit check for traversal segments moving forward, so it's top of mind.

[String] will eventually take over for a lot of existing built-in annotations and the pre-existing [NotNullOrWhiteSpace]; it covers null/empty/whitespace/min/max and regular expression tests all in one, and it will be easy to extend later (arguably, it could be extended now to handle path variations, but I decided not to).

Lastly, I've added a check for traversal segments in configured shares. The validation logic requires absolute/rooted paths already, but a careless user (or one trying to get around the absolute requirement) might use \..\ or /../ to get around this, which has no effect on Windows and results in broken shares on Linux. This follows with the previous work I've done in #1729 to guard against similar path traversal issues in other areas of the codebase.

Spun out of #1720 which has gotten too large and off-topic.