transfer function Preservation is changed to Expendable (#7243)

# Description

Fixes #7039

The Preservation of transfer method of fungible and fungibles adapters
is changed from Preserve to Expendable. So the behavior of the
TransferAsset will be consistent with the WithdrawAsset function, as in
[fungible](https://github.com/paritytech/polkadot-sdk/blob/f3ab3854

/polkadot/xcm/xcm-builder/src/fungible_adapter.rs#L217)
and [fungibles](https://github.com/paritytech/polkadot-sdk/issues/url)
adapter.

This pull request includes changes to the `fungible_adapter.rs` and
`fungibles_adapter.rs` files in the `polkadot/xcm/xcm-builder`
directory. The main change involves modifying the transfer method to use
the `Expendable` strategy instead of the `Preserve` strategy.

Changes to transfer strategy:

*
[`polkadot/xcm/xcm-builder/src/fungible_adapter.rs`](diffhunk://#diff-6ebd77385441f2c8b023c480e818a01c4b43ae892c73ca30144cd64ee960bd66L67-R67):
Changed the transfer method to use `Expendable` instead of `Preserve`.
*
[`polkadot/xcm/xcm-builder/src/fungibles_adapter.rs`](diffhunk://#diff-82221429de4c4c88be3d2976ece6475ef4fa56a32abc70290911bd47191f8e17L61-R61):
Changed the transfer method to use `Expendable` instead of `Preserve`.

---------

Co-authored-by: Francisco Aguirre <franciscoaguirreperez@gmail.com>
Co-authored-by: Adrian Catangiu <adrian@parity.io>

polkadot/xcm/xcm-builder/src/fungible_adapter.rs

@@ -20,11 +20,7 @@ use super::MintLocation;
 use core::{marker::PhantomData, result};
 use frame_support::traits::{
 	tokens::{
-		fungible,
-		Fortitude::Polite,
-		Precision::Exact,
-		Preservation::{Expendable, Preserve},
-		Provenance::Minted,
+		fungible, Fortitude::Polite, Precision::Exact, Preservation::Expendable, Provenance::Minted,
 	},
 	Get,
 };
@@ -64,7 +60,7 @@ impl<
 			.ok_or(MatchError::AccountIdConversionFailed)?;
 		let dest = AccountIdConverter::convert_location(to)
 			.ok_or(MatchError::AccountIdConversionFailed)?;
-		Fungible::transfer(&source, &dest, amount, Preserve)
+		Fungible::transfer(&source, &dest, amount, Expendable)
 			.map_err(|error| XcmError::FailedToTransactAsset(error.into()))?;
 		Ok(what.clone().into())
 	}

polkadot/xcm/xcm-builder/src/fungibles_adapter.rs

@@ -19,10 +19,7 @@
 use core::{marker::PhantomData, result};
 use frame_support::traits::{
 	tokens::{
-		fungibles,
-		Fortitude::Polite,
-		Precision::Exact,
-		Preservation::{Expendable, Preserve},
+		fungibles, Fortitude::Polite, Precision::Exact, Preservation::Expendable,
 		Provenance::Minted,
 	},
 	Contains, Get,
@@ -58,7 +55,7 @@ impl<
 			.ok_or(MatchError::AccountIdConversionFailed)?;
 		let dest = AccountIdConverter::convert_location(to)
 			.ok_or(MatchError::AccountIdConversionFailed)?;
-		Assets::transfer(asset_id, &source, &dest, amount, Preserve)
+		Assets::transfer(asset_id, &source, &dest, amount, Expendable)
 			.map_err(|e| XcmError::FailedToTransactAsset(e.into()))?;
 		Ok(what.clone().into())
 	}

prdoc/pr_7243.prdoc

+# Schema: Polkadot SDK PRDoc Schema (prdoc) v1.0.0
+# See doc at https://raw.githubusercontent.com/paritytech/polkadot-sdk/master/prdoc/schema_user.json
+
+title: 'transfer function Preservation is changed to Expendable in fungible and fungibles adapter'
+
+doc:
+  - audience: Runtime Dev
+    description: |
+      The Preservation of transfer method of fungible and fungibles adapters is changed from Preserve to Expendable. So the behavior of the TransferAsset will be consistent with the WithdrawAsset function, as in fungible and fungibles adapter.
+
+crates: 
+- name: staging-xcm-builder
+  bump: patch
\ No newline at end of file