More `xcm::v4` cleanup and `xcm_fee_payment_runtime_api::XcmPaymentApi` nits (#4355)

This PR:
- changes `xcm::v4` to `xcm::prelude` imports for coretime stuff
- changes `query_acceptable_payment_assets` /
`query_weight_to_asset_fee` implementations to be more resilient to the
XCM version change
- adds `xcm_fee_payment_runtime_api::XcmPaymentApi` to the
AssetHubRococo/Westend exposing a native token as acceptable payment
asset

Continuation of: https://github.com/paritytech/polkadot-sdk/pull/3607

Closes: https://github.com/paritytech/polkadot-sdk/issues/4297

## Possible follow-ups

- [ ] add all sufficient assets (`Assets`, `ForeignAssets`) as
acceptable payment assets ?