Polkadot's XCM config should use `WeightInfoBound` weigher

[KiChjang]

Currently, the Polkadot XCM config uses FixedWeightBounds as the weigher:

polkadot/runtime/polkadot/src/xcm_config.rs

Line 320 in d56dcfa

type Weigher = FixedWeightBounds<BaseXcmWeight, RuntimeCall, MaxInstructions>;

I don't think there is a good reason for this other than oversight, especially when Kusama, Rococo and Westend all have WeightInfoBounds as their weigher.

We should thus change the Polkadot XCM config to use WeightInfoBounds. Doing so requires benchmarking XCM instructions on the Polkadot runtime to get benchmark-weighted values for each instruction's weight.

File: runtime/polkadot/src/xcm_config.rs

[xlc]

Why this isn't implemented?

[franciscoaguirre]

I can take this

[KiChjang]

Should be fixed by #7077.