Make channel openings to system chains permissionless

[Tomen]

Currently, HRMP channel openings to system chains require acceptance of OpenGov. I believe this is not in line with the general design of the Polkadot protocol.

System chains are part of the runtime and their primary function is to optimize the configuration of the network towards lowering costs for users. If the relay/JAM is the kernel, then system chains form the operating system. In the words of @joepetrowski, they are an implementation detail.

Parachain access to relay chain features is permissionless, and by extension access to system chain features should be permissionless. System chain features offer basic functionality that should not be denied parachains on a per-case basis.

If parachains would have to request access to system chains via channels, they could get cut off features they already depend on once these features move out of the relay. This would not be consistent.

Thus I propose to fix this design issue by making channel openings to system chains permissionless.

[Tomen]

This issue was apparently already brought up by @xlc here: polkadot-fellows/RFCs#82

closing