Look into setting the max proof size weight on defaults and tests

[dmitrylavrenov]

As a follow up of #510

Related to humanode-network/substrate@61b9a4d

[MOZGIII]

From paritytech/substrate#12383:

The default max proof size is set at u64::MAX, because not all substrate-based chains require submitting PoV blocks to the relay -- standalone sovereign chains can safely ignore this weight component.

For parachains however, the proper parameter to set for the max proof size comes from the relay chain, and is stored a field called max_pov_size in this struct: paritytech/cumulus@032540d/pallets/parachain-system/src/lib.rs#L526.

We are a self-sovereign chain, and we don't send PoV blocks to the relay due to the absence of the said relay.

Thus, we can use u64::MAX everywhere.

We can consider this issue solved for now, and revisit it when/if we start dealing with PoV.