Implement RackAwarePolicy loadbalancing policy

[dkropachev]

We need to implement an API that matches RackAwarePolicy of cpp-driver that was implemented at scylladb/cpp-driver#73

[roydahan]

Do we have it as part of the list for CPP-rust parity with original cpp driver?
(I couldn't find it by its name)

[wprzytula]

Do we have it as part of the list for CPP-rust parity with original cpp driver? (I couldn't find it by its name)

No; apparently, the list does not contain our cpp-driver's API extensions, because it predates them.

[roydahan]

Do we have it as part of the list for CPP-rust parity with original cpp driver? (I couldn't find it by its name)

No; apparently, the list does not contain our cpp-driver's API extensions, because it predates them.

@muzarski can you please add it to the spreadsheet we track the cpp-rust missing functionalities.

[muzarski]

Do we have it as part of the list for CPP-rust parity with original cpp driver? (I couldn't find it by its name)

No; apparently, the list does not contain our cpp-driver's API extensions, because it predates them.

@muzarski can you please add it to the spreadsheet we track the cpp-rust missing functionalities.

Done, added entries for cass_cluster_set_load_balance_rack_aware[_n] missing API functions