upgrade: fix upgrading from schema 1.6.9

This commit fixes some cases of upgrading schema from 1.6.9:

1. Fix updating empty password for users. In 1.6 credentials were array
   in _user, in 1.7.5 they became map.

2. Automatically update the format of user spaces. Format of system
   spaces have been properly fixed during upgrade to 1.7.5. However,
   commit 519bc82e ("Parse and validate space formats") introduced
   strict checking of format field in 1.7.6. So, the format of user
   spaces should be also fixed.

Back in 1.6 days, it was allowed to write anything in space format.
This commit only fixes valid uses of format:
    {name = 'a', type = 'number'}
    {'a', type = 'number'}
    {'a', 'num'}
    {'a'}

Invalid use of format (e.g. {{}}, or {{5, 'number'}} will cause error
anyway. User has to fix the format on old version and only after that
start a new one.

This commit also introduces the test, which checks, that we can
properly upgrade from 1.6.9 to the latest versions, at least in basic
cases.

Closes #10180

NO_DOC=bugfix

(cherry picked from commit f69e2ae488b3620e31f1a599d8fb78a66917dbfd)