fix(import): directly format generated sql with its args in import phase

When we generate SQL from RQL in CubicWeb, each litteral are passed as args when executing the SQL. In our case, when we create tsfacets tables, we can have a lot of litteral involved in RQL, which sometimes can lead to have two times the same key, since all SQL parts are generated one by one.

To avoid this, each time we build a SQL part, we directly format it with the args (only in import phase, so we can't have strange SQL injection).