M2: Tests get_tables() get_indexes() get_columns()

These methods should be also tested, to check they return the same information for all drivers we implement.

get_tables()
get_indexes()
get_coumns()

specially things like defaults and enums are critical and I expect we'll find some problems with them across DBs. Any problem here should be reported to MDL-14957 (where the task of fixing those functions is addressed).

Ciao