MB-10382: change upr-related stats format

The vbucket-seqno stats will be showed in a way consistent
with existent ep-engine stats, for example:

`vbucket-seqno 1`:
vb_1:high_seqno: 107
vb_0:vb_uuid 2723958720985

Change-Id: I8d500cb2c2247229584a855e103cd6c91f6dd397
Reviewed-on: http://review.couchbase.org/34647
Tested-by: Junyi Xie <junyi.couchbase@gmail.com>
Reviewed-by: David Liao <david.liao@couchbase.com>