Only gofer filesystem was calling vfs.CheckSetStat for
vfs.FilesystemImpl.SetStatAt and vfs.FileDescriptionImpl.SetStat.
Updates #1193, #1672, #1197
PiperOrigin-RevId: 301226522
Because the abi will depend on the core types for marshalling (usermem,
context, safemem, safecopy), these need to be flattened from the sentry
directory. These packages contain no sentry-specific details.
PiperOrigin-RevId: 291811289