test: add the extended transactional DDL tests

Added more tests for various scenarios of the transactional DLL usage:
1. A DDL transaction which creates a space, formats it to have an
   integer column, fills it with some data, changes the format to
   'any', changes the data values to 'string', and changes the format
   to 'string'.
2. A DDL transaction that creates a space, user, grants privileges to
   the user to use the new space and accesses the space on behalf of
   the new user.
3. Creation of a space and its secondary indexes in one transaction.
4. Creation of a space with a sequence attached in one transaction.
5. A DDL transaction which sets the on_rollback trigger and creates a
   space, the space triggers, inserts a bunch of data and then commits
   or rolls back.
6. Transactional drop of a space with various indexes, field and tuple
   constraints and a sequence attached. The formers are also created
   in a single transaction.

Closes #4349

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