Update password hashes from SHA-256 to Argon2id

These days salted SHA-256 is considered quite weak for passwords.

Transparently upgrade existing hashes upon login.

Bump cmake requirement to able to use IMPORTED_TARGET, this will allow
further cleanup in next commits.

configure

@@ -83,6 +83,7 @@ tristate('cyrus')
 tristate('charset', 'ICU')
 tristate('tcl')
 tristate('i18n')
+tristate('argon')
 
 class HandlePython(argparse.Action):
     def __call__(self, parser, namespace, values, option_string=None):