Note, this patch will be backported to 2.10 so we add upgrade function
for 2.10.5, not for 2.11.0.

Needed for #7858

@TarantoolBot document
Title: Document `_space_sequence` and `_vspace_sequence` system spaces

The `_space_sequence` system space was added long time ago (in 1.7.5)
along with the `_sequence` and `_sequence_data` system spaces, but it
was never documented. The space is used to attach sequences to spaces
and has the following fields:
 1. 'id', type 'unsigned'. Space id.
 2. 'sequence_id', type 'unsigned'. Id of the attached sequence.
 3. 'is_generated', type 'boolean'. True if the sequence was created
    automatically (`space:create_index('pk', {sequence = true})`)
 4. 'field', type 'unsigned'. Id of the space field that is set using
    the attached sequence.
 5. 'path', type 'string'. Path to the data within the field that is set
    using the attached sequence.

The `_vspace_sequence` is a system space view of the `_space_sequence`
space that, like any other system space view, shows only rows accessible
by the current user. It will be introduced in Tarantool 2.10.5.