Improve block number related logic in integration tests

[apopiak]

There were a bunch of issues with block numbers in integration tests recently.

I think we should rewrite e.g. https://github.com/galacticcouncil/HydraDX-node/blob/1e9b8f23c3abfdc2684c67652697165f6a47da5b/integration-tests/src/polkadot_test_net.rs#L356 and https://github.com/galacticcouncil/HydraDX-node/blob/1e9b8f23c3abfdc2684c67652697165f6a47da5b/integration-tests/src/oracle.rs#L20 (and the others)

into something that bumps both the relay chain number and the HydraDX number, with both of them being different (relay should be higher).