Expose all GI enum and flags types

Add new types for GIDirection, GITransfer, GIArrayType, GIScopeType,
GIVFuncInfoFlags, GIFieldInfoFlags, GIFuncitonInfoFlags, GITypeTag, and
GInfoType. These types are found in the gi._gi module exposed without the
"GI" prefix and contain all of their values as class attributes. e.g.
gi._gi.Transfer.EVERYTHING.

https://bugzilla.gnome.org/show_bug.cgi?id=709008