Fix performance issues of the "UpdateStatus" operation when called on the whole Content folder

[SRombautsU]

This is a less common scenario, typically calling the Submit Content, Revert All or Refresh commands from the global source control menu.

• Remove the call to IterateDirectoryRecursively() that was taking a few seconds for each 100k assets
• Rename ParseDirectoryStatusResultForDeleted() to ParseDirectoryStatusResult() and use it to parse the list of status results in the case of a whole directory status update

Also updated the method headers to better explain the asymetry