A0-1847: Add support for disuniting aura and alephbft

[youPickItUp]

Testing section says

However it’s important to also test it with a local node, to see if it also works with non-trivial settings concerning both commitees (on testnet both committees are currently the same, so it’s not interesting).

I wasn't able to test it localy for interesting settings. @kostekIV could you guide me how to do it, or test it yourself?

[kostekIV]

You need to make a sudo call Elections.change_validators that can be done by tab https://test.azero.dev/#/extrinsics (obviously use the local one :P). Change the committee seats to have different (smaller )values for non_reserved_finality_committe. Im ooo today If this is not helpful :P I will test it tomorrow