Decouple TransactionPayment from polynomial

[kianenigma]

Sorry @nazar-pc I deleted my comment cause I didnt read any code, but now I did.

It is strange to me that there is a WeightToFeePolynomial trait at all.

Seems the trait should simply be WeightToFee with a single function fn calc that should be implemented, and this is what should be required in the pallet.

Then there should be a subtrait WeightToFeePolynomial, or just a struct, which implements WeightToFee but in the case of a polynomial.

Does that make sense? Then you can simply have Identity be the true identity without any polynomial bs.

Originally posted by @shawntabrizi in #11226 (comment)