net.box: add info about sequence to remote space object

A remote space object presented by a net.box connection mimics the API
of a local space object presented by box.space. Currently, it misses
information about sequences. Let's add it.

Note, we have to handle the case when the recently introduced
_vspace_sequence system space view is missing on the remote host.
To check that this works correctly, we reuse the 2.10.4 test data
created by commit 1c33484d ("box: add auth_history and
last_modified fields to _user space"). We also add the 'gen.lua'
that can be used to regenerated the data.

Closes #7858

NO_DOC=bug fix