Maximal proof_size

After some research, I noticed that our chain is underutilized because the proof_size parameter is limited to 5 * 1024 * 1024 (https://git.duniter.org/nodes/rust/duniter-v2s/-/blob/master/runtime/gdev/src/parameters.rs#L27). For a solo chain, this limit can be ignored (https://github.com/paritytech/polkadot-sdk/blob/cbe45121c9a7bb956101bf28e6bb23f0efd3cbbf/templates/solochain/runtime/src/lib.rs#L139-L141), which means we are underusing the chain's resources because the proof_size quickly becomes a limiting factor on the ref_time.

See polkadot-sdk/substrate/frame/system/src/extensions/check_weight.rs at cbe45121c9a7bb956101bf28e6bb23f0efd3cbbf · paritytech/polkadot-sdk · GitHub for more details on how Substrate calculates weights and lengths before execution.