Migrate fee payment from Currency to fungible (#2292)

Part of https://github.com/paritytech/polkadot-sdk/issues/226 
Related https://github.com/paritytech/polkadot-sdk/issues/1833

- Deprecate `CurrencyAdapter` and introduce `FungibleAdapter`
- Deprecate `ToStakingPot` and replace usage with `ResolveTo`
- Required creating a new `StakingPotAccountId` struct that implements
`TypedGet` for the staking pot account ID
- Update parachain common utils `DealWithFees`, `ToAuthor` and
`AssetsToBlockAuthor` implementations to use `fungible`
- Update runtime XCM Weight Traders to use `ResolveTo` instead of
`ToStakingPot`
- Update runtime Transaction Payment pallets to use `FungibleAdapter`
instead of `CurrencyAdapter`
- [x] Blocked by https://github.com/paritytech/polkadot-sdk/pull/1296,
needs the `Unbalanced::decrease_balance` fix

substrate/frame/treasury/src/lib.rs

@@ -76,6 +76,8 @@ mod benchmarking;
 #[cfg(test)]
 mod tests;
 pub mod weights;
+use core::marker::PhantomData;
+
 #[cfg(feature = "runtime-benchmarks")]
 pub use benchmarking::ArgumentsFactory;
 
@@ -1120,3 +1122,15 @@ impl<T: Config<I>, I: 'static> OnUnbalanced<NegativeImbalanceOf<T, I>> for Palle
 		Self::deposit_event(Event::Deposit { value: numeric_amount });
 	}
 }
+
+/// TypedGet implementaion to get the AccountId of the Treasury.
+pub struct TreasuryAccountId<R>(PhantomData<R>);
+impl<R> sp_runtime::traits::TypedGet for TreasuryAccountId<R>
+where
+	R: crate::Config,
+{
+	type Type = <R as frame_system::Config>::AccountId;
+	fn get() -> Self::Type {
+		<crate::Pallet<R>>::account_id()
+	}
+}