feat: add weights v2

[wischli]

fixes KILTProtocol/ticket#2173

Working branch against Substrate/Polkadot/Cumulus master upstream with goal:

• Converts 1d weight (u64) to 2d struct

pub struct Weight {
	/// The computational time used to execute some logic based on reference hardware.
	ref_time: u64,
	/// The size of the proof needed to execute some logic.
	proof_size: u64,
}

Checklist:

• I have verified that the code works
  • No panics! (checked arithmetic ops, no indexing array[3] use get(3), ...)
• I have verified that the code is easy to understand
  • If not, I have left a well-balanced amount of inline comments
• I have left the code in a better state
• I have documented the changes (where applicable)

[wischli]

Closing due to merging the current changes in #416