Add HRMP Cancel variant to hrmp_manage

[Agusrodri]

What does it do?

This PR introduces the possibility to cancel a request within hrmp_manage() extrinsic present in xcm-transactor pallet.

Changes

• Added Cancel variant to HrmpOperation enum.

pub enum HrmpOperation {
		InitOpen(HrmpInitParams),
		Accept {
			para_id: ParaId,
		},
		Close(HrmpChannelId),
		Cancel {
			channel_id: HrmpChannelId,
			open_requests: u32,
		},
	}

• Added CancelOpenChannel variant to HrmpAvailableCalls enum.

pub enum HrmpAvailableCalls {
	InitOpenChannel(ParaId, u32, u32),
	AcceptOpenChannel(ParaId),
	CloseChannel(HrmpChannelId),
	CancelOpenChannel(HrmpChannelId, u32),
}

• Also modified hrmp_encode_call() implementation of polkadot, kusama and westend relay encoders to accept these new variants.

[girazoki]

I dont think Adding an enum variant is a breaking change

[girazoki]

looks good

[girazoki]

Maybe you can add the variant to https://github.com/PureStake/moonbeam/blob/master/precompiles/relay-encoder/RelayEncoder.sol too. Or we can leave it for a future pr

[Agusrodri]

Maybe you can add the variant to https://github.com/PureStake/moonbeam/blob/master/precompiles/relay-encoder/RelayEncoder.sol too. Or we can leave it for a future pr

I will open a new ticket and a new PR for that, to decouple changes a bit more.