Folders beginning with two periods are incorrectly collapsed by FPaths::CollapseRelativeDirectories

The Function FPaths::CollapseRelativeDirectories assumes that any instance of the characters "/.." are a relative path to the parent directory, and removes them along with the preceding directory. However, it's valid in Windows to create a folder that beings with two periods, meaning the resulting path will be misinterpreted by our collapse function. This caused an issue with a licensee where a user had put two periods before their username, resulting in the user directory "C:/Users/..username/somefolder" resolving as "C:username/somefolder".

Solving this would likely require looking ahead at the next character following "/.." to see if it is a slash or if it's at the end of the path. Otherwise, it should be ignored.

Run the following code, and observe the output:

FString Path = "C:/My/./Path/..FolderName";
FPaths::CollapseRelativeDirectories(Path);
UE_LOG(LogTemp, Warning, TEXT("Output: %s"),*Path);

Expected output: "C:/My/Path/..FolderName"

Actual output: "C:/My/.FolderName"