Allow localhost enabling to be a parameter

[AdityaSripal]

Perhaps we should add a parameter that allows chains to enable or disable localhost on their chain

This would then be checked in the localhost verification case to ensure it is enabled. Localhost verification should fail if the parameter is set to false

EDIT from @chatton

Additional tasks to be completed after the internal audit:

• Use allowed clients list to dynamically enable/disable and client type.
• Add Unauthorized status for light clients. This status should be returned if the client type is not in the allowed_list
• Add light client status checks in ChanOpenInit and ConnOpenInit.

[colin-axner]

There already is a parameter in 02-client, closing

[colin-axner]

One possible approach:

• add a enable/disable field to client state
• add msg to change this value (gov v1 msg, authority is only gov module)
• update localhost client state upon execution
• use client state field in Status

[damiannolan]

I think in order to do gov v1 message execution it will incur an API breaking change to the ibc core NewKeeper() function.

SDK modules which have migrated to use self managed params now take the additional arg to NewKeeper() functions: authority and store it as a field on the keeper. Where authority is the gov module account address.

See here and below where the additional authority arg is added

[colin-axner]

Could we preemptively get the API breaking change in v7 (without additional logic acting on the authority)? Or does it feel too late in the cycle for that?

[damiannolan]

Sounds good to me. I think if its just changing the core NewKeeper function to accept an additional arg and store it as a field on the keeper then its totally fine

[chatton]

closing this as #3196 has been merged into the feature branch.