Simplify economy system in metadata chain

Is your feature request related to a problem? Please describe.

I'm always frustrated when we have unnecessary economy for pure data storage.

Describe the solution you'd like

Drop anything that will not be used as an economy model in metadata chain.
The best thing that may happen: no GAS contract, simplified NEO contract that only stores commitee, notary contract should only be presented if it is impossible/hard to avoid it, etc.

Describe alternatives you've considered

It works already.

Additional context

You need to implement custom Neo contract (like you did it with custom Gas). This contract should implement minimal required functionality for meta chain: committee tracking and committee witness checking, that's it (although I'm not sure whether we need dynamic committee at meta chain; let's start with static set of keys). The rest of INEO functionality should be stubbed. Voting should be dropped.

Originally posted by @AnnaShaleva in https://github.com/nspcc-dev/neofs-node/pull/3759#discussion_r2722635286

Start by reviewing the discussion in pull request #3759 and the existing custom Gas implementation. Define the smallest meta-chain contract that tracks the committee and checks committee witnesses, while confirming which INEO functionality can be stubbed and whether the notary contract can be avoided; done means voting and unused economy functionality are removed.