Deprecate --interop-genesis-state

[rkapka]

What type of PR is this?

Cleanup

What does this PR do? Why is it needed?

The flag --interop-genesis-state does not work. Running interop with this flag results in the following error:

Deposit contract: 0x4242424242424242424242424242424242424242
could not get genesis block root: OriginGenesisRoot: not found in db

Running interop with --genesis-state works properly and this is the flag that should be used moving forward.

[kasey]

I think the pattern for deprecation is deleting the flag from it's home in cmd/beacon-chain and adding a new no-op flag with a deprecation warning here: ./config/features/deprecated_flags.go

Since we're close to a major version breaking change opportunity, and this is an easy removal to justify given the normal genesis state flag works, I would suggest we go ahead and also remove the code that currently uses InteropGenesisStateFlag. cc @terencechain as he I think he does a lot with interop and might know if there are things that could break from this, and @rauljordan to check if his interop docker stuff uses this flag.

[rkapka]

I think the pattern for deprecation is deleting the flag from it's home in cmd/beacon-chain and adding a new no-op flag with a deprecation warning here: ./config/features/deprecated_flags.go

Ah yes, I forgot about this. Also I agree that maybe we should just remove this all together instead of deprecating.

[nisdas]

We can possibly split the removal of code that uses InteropGenesisStateFlag into another PR. @rkapka we prob should follow our pattern for flag deprecation in this PR as kasey mentioned, since we will probably be having another release until v4. Once that is done we can merge it in

[terencechain]

Nice removal indeed but we need to fix the tests