WL#4497: I_S: cleanup INFORMATION_SCHEMA.FILES

There are some fields in INFORMATION_SCHEMA.FILES which purely relate to
tablespaces. When WL#2511 is ready it'll provide detailed information about
tablespaces and there will be duplicating fields. These fields should be removed
from I_S.FILES.


References:
architecture forum thread
"Notes from the architecture meeting April 11-12"
https://intranet.mysql.com/secure/forum/read.php?54,98909,98909#msg-98909