Give ConvertPermissionAlgorithm ability to switch to MultiValueMap to file system store

• Type: Bug
• Status: Closed
• Resolution: Fixed
• Affects Version/s: 5.2.3, 5.2.9 EE, 6.0.6 GA, 6.0.11 EE
• Fix Version/s: 5.2.X EE, --Sprint - SP, 6.0.12 EE, 6.1.0 CE RC1
• Component/s: Core Infrastructure, Core Infrastructure > Upgrade Framework, User Management, User Management > Roles
• Labels: None
• Branch Version/s:
  6.0.x, 5.2.x

Currently ConvertPermissionAlgorithm is using an Apache MultiValueMap. However, if there is too many entries to convert, it can get an out of memory error. Allow ability to switch to file system store of MultiValueMap.