Check for HRMP or VMP channels between two chains

[Szegoo]

We should introduce a new class that will be responsible for figuring out whether there is a channel between two blockchains.

EDIT: We do not need to know the channel type, we just essentially need a function that will return a boolean representing whether there exists a channel between two blockchains. Making a separate class for this might not even be needed.

[cuteolaf]

We need RPC url of the relay chain.