exfat: style fixes only
exfat: limit backup volume name to 11 characters
exfat: Set the mountpoint to same as volume name

Fixes #10501

* update copyright headers, attribute to Haiku, Inc. add authors
* volume_name gets filled out by a utility function in Utility.cpp
* update exfat_entry
  - rename name_label to just label
  - adjust volume_label to have 11 uint16 chars plus 8 uint8 reserved
  - add guid partition info
* Added a couple new entry type defines
* fName is 34 bytes long which fits the 11 3-byte UTF-8 chars and a \0