asset-hub-polkadot: use inmemorydb weights

[alexggh]

Modify asset-hub-polkadot to use the read/write costs computed in validate block on validator reference hardware, since these are weights that guarantee the blocks will pass validation and make it on the relay chain.

This were obtained with the benchmark created here: paritytech/polkadot-sdk#8069.

Part of: #800

[alexggh]

@claravanstaden with this PR I see tests::snowbridge_v2_config::asset_hub_weights_should_be_equal_or_gte_bridge_hub_weights fails, because reads/writes weights just became lower, could you give me a bit more context about this test, is it mandatory for asset_hub_weights to always be bigger that bridge_hub for this extrinscs or is it there just to make sure things are kept in sync ?

If this is mandatory I can do something like this to make sure the weights for extrinsics snowbridge_pallet_system_backend.rs don't get affected.

        fn transact_register_token() -> Weight {
                Weight::from_parts(53_009_000, 0)
                        .saturating_add(Weight::from_parts(0, 4115))
-                       .saturating_add(T::DbWeight::get().reads(4))
-                       .saturating_add(T::DbWeight::get().writes(4))
+                       .saturating_add(RocksDbWeight::get().reads(4))
+                       .saturating_add(RocksDbWeight::get().writes(4))

[claravanstaden]

Hey @alexggh!

is it mandatory for asset_hub_weights to always be bigger that bridge_hub for this extrinscs or is it there just to make sure things are kept in sync ?

Yes, it is mandatory for the AH weights to be equal or bigger than the BH extrinsics, because these AH extrinsics call a corresponding extrinsic on BH. So the caller needs to cover both the AH and BH extrinsic costs.

[alexggh]

Hey @alexggh!

is it mandatory for asset_hub_weights to always be bigger that bridge_hub for this extrinscs or is it there just to make sure things are kept in sync ?

Yes, it is mandatory for the AH weights to be equal or bigger than the BH extrinsics, because these AH extrinsics call a corresponding extrinsic on BH. So the caller needs to cover both the AH and BH extrinsic costs.

Alright totally makes sense, then I'll keep them that same e2c5830, let me know if you have any concern.

[claravanstaden]

@alexggh perfect!

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