box: introduce space:alter()

There was no way to change certain space parameters without its
recreation or manual update of internal system space _space. Even
if some of them were legal to update: field_count, owner, flag of
being temporary, is_sync flag.

The patch introduces function space:alter(), which accepts a
subset of parameters from box.schema.space.create which are
mutable, and 'name' parameter. There is a method space:rename(),
but still the parameter is added to space:alter() too, to be
consistent with index:alter(), which also accepts a new name.

Closes #5155

@TarantoolBot document
Title: New function space:alter(options)

Space objects in Lua (stored in `box.space` table) now have a new
method: `space:alter(options)`.

The method accepts a table with parameters `field_count`, `user`,
`format`, `temporary`, `is_sync`, and `name`. All parameters have
the same meaning as in `box.schema.space.create(name, options)`.

Note, `name` parameter in `box.schema.space.create` is separated
from `options` table. It is not so in `space:alter(options)` -
here all parameters are specified in the `options` table.

The function does not return anything in case of success, and
throws an error when fails.

From 'Synchronous replication' page, from 'Limitations and known
problems' it is necessary to delete the note about "no way to
enable synchronous replication for existing spaces". Instead it
is necessary to say, that it can be enabled using
`space:alter({is_sync = true})`. And can be disabled by setting
`is_sync = false`.
https://www.tarantool.io/en/doc/2.5/book/replication/repl_sync/#limitations-and-known-problems

The function will appear in >= 2.5.2.