CORE-5029 Added recursive path count validations.

Updated the /secured/filesystem endpoints move, rename, delete, and restore to validate the total number of items and subdirectories contained in any paths requested before performing their actions.
Moved this validation check for move-contents, delete-contents, and restore-all into their pre-hook functions.
Refactored the services.filesystem.validators/num-paths-okay? and validate-num-paths functions so that all of the validate-num-paths* functions can use a common validate-path-count function that will throw the same exception.