`CollectionPathV2`: even stricter checks

[s373r]

Expectations

• ///foo////bar -- this path should be processed as /foo/bar
• /foo/bar/ -- If the path points to a directory, there should be an error.
• ../foo -- relative paths should be prohibited

[sergiimk]

Current logic prohibits:

• ///foo////bar - this will be considered as containing empty path segments
• /foo/bar/ - same - empty segment at the end

And path like ../foo - will be viewed as .. being a directory name.

I'm not sure we should change the current logic - I'd rather not have the full semantics of a file system on Kamu side, but have users treat paths similarly to S3 paths instead - as just strings with certain separators.

[s373r]

Since the ticket was created when the previous implementation of CollectionPathV2 was in place -- let's just close this ticket then.