feat: Permissioned collators

[Ad96el]

fixes#3822

This PR introduces permissioned collators to the Peregrine and Spirtinet runtimes. The council or governance is now allowed to add and remove members through the newly deployed pallet-membership. This pallet is then used by a new session manager implementation. The old session manager implementation remains untouched—it's only moved out of the runtime.

After the migration, the parachain-staking pallet becomes essentially obsolete, as collators no longer receive rewards for block production.

A follow-up PR will reduce rewards in the parachain-staking pallet accordingly.

The round information (which determines session length) still resides in the parachain-staking pallet. Before it can be removed, a new source for round length must be implemented—either directly in the runtime or via a custom pallet that includes collator information.

How to test

• Navigate to the zombienet directory and spin up a Peregrine runtime.
• Perform the runtime upgrade (sudo -> system -> set_code).
• Add a new collator via sudo or start a council motion (sudo -> permissionedCollators -> add_member).
• Force a new round (sudo -> parachainStaking -> forceNewRound).
• Verify in the session pallet that the new collator is queued. (To use a new collator, spin up a node with the correct keys. Using an existing collator is usually easier.)
• Force another new round.
• Only the new collator should be producing blocks now.

[Ad96el]

I decided to add the benchmarking in this PR.

[ntn-x2]

Minor things. Also, it seems the PR description is outdated, since I can't see where the staking pallet is being used? Session length has a fixed duration now, so the only thing that the staking pallet does, is to provide collators until there is a well formed collator set (meaning non empty and with all session keys set) that is returned by the new session manager.

[ntn-x2]

I think a different error message depending on which condition is false would massively reduce headaches in the future.

[Ad96el]

Fair point. I created a new PR: #887