XCM RFC: Better fee handling

Over the last weeks, we’ve seen a bunch of xcm-related bugs on Kusama and Polkadot because of the addition of delivery fees.

Discussions have been going around for integrating delivery fees better in the XCM format itself, making sure these types of issues are fixed once and for all.

In the spirit of Improve XCM development and release process, I opened an RFC in the XCM format repository where we can discuss a solution.

I invite everyone to participate.