Add XcmPayment runtime API

[Agusrodri]

What does it do?

Adds the new runtime API called XcmPaymentApi, which allows to fetch the following information:

• A list of allowed assets for XCM execution payment.
• A weight-to-asset fee conversion (as long as the indicated asset is allowed to be used for execution payment).
• Retrieves the weight estimation for a specific XCM message.
• Retrieves the amount of XCM delivery fees (if any) for a specific XCM message to a specific destination.

More context on: paritytech/polkadot-sdk#3607

[github-actions]

Coverage Report

@@                     Coverage Diff                     @@
##           master   agustin-xcm-payment-api      +/-   ##
===========================================================
+ Coverage   81.10%                    81.26%   +0.16%     
+ Files         274                       301      +27     
+ Lines       80576                     85781    +5205     
===========================================================
+ Hits        65348                     69704    +4356     
+ Misses      15228                     16077     +849     

Files Changed	Coverage
/client/rpc/finality/src/lib.rs	95.92% (+7.78%)	🔼
/pallets/parachain-staking/src/lib.rs	91.73% (-0.01%)	🔽
/pallets/parachain-staking/src/mock.rs	97.65% (+0.02%)	🔼
/pallets/parachain-staking/src/tests.rs	91.39% (+0.03%)	🔼
/precompiles/xcm-transactor/src/v1/mod.rs	87.95% (+0.45%)	🔼
/precompiles/xcm-transactor/src/v2/mod.rs	76.42% (-2.22%)	🔽
/precompiles/xcm-transactor/src/v3/mod.rs	83.33% (-2.26%)	🔽
/precompiles/xcm-utils/src/lib.rs	90.98% (-0.69%)	🔽
/runtime/common/src/apis.rs	28.40% (-2.12%)	🔽

Coverage generated Wed Jul 10 22:13:43 UTC 2024

[RomarQ]

About the test, could we use the fees calculated and do an xcm call to make sure the estimated value is enough?

[Agusrodri]

About the test, could we use the fees calculated and do an xcm call to make sure the estimated value is enough?

@RomarQ I just added two tests (one for native fees and another one for foreign fees) in 391b636 :)