Fix bind() on overlays.
Fix bind() on overlays.

InodeOperations.Bind now returns a Dirent which will be cached in the Dirent
tree.

When an overlay is in-use, Bind cannot return the Dirent created by the upper
filesystem because the Dirent does not know about the overlay. Instead,
overlayBind must create a new overlay-aware Inode and Dirent and return that.
This is analagous to how Lookup and overlayLookup work.

PiperOrigin-RevId: 208670710
Change-Id: I6390affbcf94c38656b4b458e248739b4853da29

google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor