We are going to utilize primary key definition during space upgrade in
order to verify primary key invariant. So we need it to be stored in
space_upgrade metadata. Let's extend space_upgrade_new() signature and
pass there primary key definition. Also patch moves space_upgrade_new()
call a bit lower through code - now it's called after all indexes are
assigned (to simplify extraction of primary key definition).
Moreover, in order to print pretty error message during space upgrade
we should keep space in struct space_upgrade.

NO_DOC=ee
NO_TEST=ee
NO_CHANGELOG=ee