Improved transaction payment pallet

[xlc]

Currently transaction payment pallet made a lot of assumption of how the fee is calculated and charged and made it not suitable for many chains.

The asset tx payment pallet is also not generic enough to be reusable.

Parachain teams are making their own fork to support fee payments with different tokens. It will be good if we can have a generic transaction payment pallet to abstract common code to avoid duplicated code and at same time to be generic enough so that parachain teams can extend the pallet, instead of forking it.

Examples from parachains:

Acala: https://github.com/AcalaNetwork/Acala/blob/master/modules/transaction-payment/src/lib.rs
Bifrost: https://github.com/bifrost-finance/bifrost/blob/develop/pallets/flexible-fee/src/lib.rs
HydraDX: https://github.com/galacticcouncil/warehouse/blob/main/transaction-multi-payment/src/lib.rs

[Polkadot-Forum]

This issue has been mentioned on Polkadot Forum. There might be relevant details there:

https://forum.polkadot.network/t/polkadot-summit-24-boosting-the-developer-experience/7202/3