Allow to disable schema fetch

[olegrok]

I suggest to implement an option that disables schema fetching.

As it was implemented in netbox (tarantool/tarantool#4789).
And as it was implemented in Go connector:
https://github.com/tarantool/go-tarantool/blob/de95e3184df6bde148e7cc87229572d4247f599b/connection.go#L199-L201