Some of our code sets binVersion for each node in ReplSetTest options. This behaviour is wrong and we need to throw an explicit error when it happens.

Here we take our node-specific options and merge them into options object:
https://github.com/mongodb/mongo/blob/05518f9b480f4f65fc963b47ef4cf45c9e4807b5/src/mongo/shell/replsettest.js#L2782

And in the next code block we override binVersion with "latest" or useRandomBinVersionsWithinReplicaSet: https://github.com/mongodb/mongo/blob/05518f9b480f4f65fc963b47ef4cf45c9e4807b5/src/mongo/shell/replsettest.js#L2795

We also state that setting both binVersion and useRandomBinVersionsWithinReplicaSet is incorrect, but we check that before we merge node-specific options:
https://github.com/mongodb/mongo/blob/05518f9b480f4f65fc963b47ef4cf45c9e4807b5/src/mongo/shell/replsettest.js#L2754

We also set FCV based on node-specific binVersion values: 
https://github.com/mongodb/mongo/blob/05518f9b480f4f65fc963b47ef4cf45c9e4807b5/src/mongo/shell/replsettest.js#L1363
https://github.com/mongodb/mongo/blob/05518f9b480f4f65fc963b47ef4cf45c9e4807b5/src/mongo/shell/replsettest.js#L1435

Which leads to an interesting situation when we can think that we started 6.0, but actually we started 6.2 with 6.0 FCV