Resolve Credit to Account impls of OnUnbalanced trait (paritytech#1876

)

Implements the `OnUnbalanced` trait to resolve received credits to the
specified account. Credits that fail to resolve are dropped.

### Motivation 
Throughout the codebase, several types implement the trait with the same
behavior. While some currently utilize older currency trait, a migration
to the new fungible/s is anticipated for all. Examples:
[1](https://github.com/paritytech/polkadot-sdk/blob/c29c233dbb581ba0bed162358e76a82210f0c721/cumulus/parachains/common/src/impls.rs#L37),
[2](https://github.com/paritytech/polkadot-sdk/blob/c29c233dbb581ba0bed162358e76a82210f0c721/polkadot/runtime/common/src/impls.rs#L36),
[3](https://github.com/paritytech/polkadot-sdk/blob/c29c233dbb581ba0bed162358e76a82210f0c721/substrate/bin/node/runtime/src/impls.rs#L40),
[4](https://github.com/paritytech/polkadot-sdk/blob/c29c233dbb581ba0bed162358e76a82210f0c721/substrate/bin/node/runtime/src/lib.rs#L1969),
[5](https://github.com/paritytech/polkadot-sdk/blob/c29c233dbb581ba0bed162358e76a82210f0c721/substrate/frame/broker/src/mock.rs#L198),
[6](https://github.com/paritytech/polkadot-sdk/blob/c29c233dbb581ba0bed162358e76a82210f0c721/substrate/frame/society/src/lib.rs#L2031),
[7](https://github.com/paritytech/polkadot-sdk/blob/c29c233dbb581ba0bed162358e76a82210f0c721/substrate/frame/treasury/src/lib.rs#L1118)

substrate/frame/support/src/traits/tokens/imbalance.rs

@@ -25,7 +25,7 @@ use sp_std::ops::Div;
 mod on_unbalanced;
 mod signed_imbalance;
 mod split_two_ways;
-pub use on_unbalanced::OnUnbalanced;
+pub use on_unbalanced::{OnUnbalanced, ResolveAssetTo, ResolveTo};
 pub use signed_imbalance::SignedImbalance;
 pub use split_two_ways::SplitTwoWays;
 

substrate/frame/support/src/traits/tokens/imbalance/on_unbalanced.rs

@@ -17,7 +17,9 @@
 
 //! Trait for handling imbalances.
 
-use crate::traits::misc::TryDrop;
+use frame_support::traits::{fungible, fungibles, misc::TryDrop};
+use sp_core::TypedGet;
+use sp_std::marker::PhantomData;
 
 /// Handler for when some currency "account" decreased in balance for
 /// some reason.
@@ -53,3 +55,29 @@ pub trait OnUnbalanced<Imbalance: TryDrop> {
 }
 
 impl<Imbalance: TryDrop> OnUnbalanced<Imbalance> for () {}
+
+/// Resolves received asset credit to account `A`, implementing [`OnUnbalanced`].
+///
+/// Credits that cannot be resolved to account `A` are dropped. This may occur if the account for
+/// address `A` does not exist and the existential deposit requirement is not met.
+pub struct ResolveTo<A, F>(PhantomData<(A, F)>);
+impl<A: TypedGet, F: fungible::Balanced<A::Type>> OnUnbalanced<fungible::Credit<A::Type, F>>
+	for ResolveTo<A, F>
+{
+	fn on_nonzero_unbalanced(credit: fungible::Credit<A::Type, F>) {
+		let _ = F::resolve(&A::get(), credit).map_err(|c| drop(c));
+	}
+}
+
+/// Resolves received asset credit to account `A`, implementing [`OnUnbalanced`].
+///
+/// Credits that cannot be resolved to account `A` are dropped. This may occur if the account for
+/// address `A` does not exist and the existential deposit requirement is not met.
+pub struct ResolveAssetTo<A, F>(PhantomData<(A, F)>);
+impl<A: TypedGet, F: fungibles::Balanced<A::Type>> OnUnbalanced<fungibles::Credit<A::Type, F>>
+	for ResolveAssetTo<A, F>
+{
+	fn on_nonzero_unbalanced(credit: fungibles::Credit<A::Type, F>) {
+		let _ = F::resolve(&A::get(), credit).map_err(|c| drop(c));
+	}
+}