[pallet-xcm] Adjust benchmarks (teleport_assets/reserve_transfer_assets) not relying on ED (#3464)

## Problem
During the bumping of the `polkadot-fellows` repository to
`polkadot-sdk@1.6.0`, I encountered a situation where the benchmarks
`teleport_assets` and `reserve_transfer_assets` in AssetHubKusama
started to fail. This issue arose due to a decreased ED balance for
AssetHubs introduced
[here](https://github.com/polkadot-fellows/runtimes/pull/158/files#diff-80668ff8e793b64f36a9a3ec512df5cbca4ad448c157a5d81abda1b15f35f1daR213),
and also because of a [missing CI
pipeline](https://github.com/polkadot-fellows/runtimes/issues/197) to
check the benchmarks, which went unnoticed.

These benchmarks expect the `caller` to have enough:
1. balance to transfer (BTT)
2. balance for paying delivery (BFPD).
 
So the initial balance was calculated as `ED * 100`, which seems
reasonable:
```
const ED_MULTIPLIER: u32 = 100;
let balance = existential_deposit.saturating_mul(ED_MULTIPLIER.into());`
```
The problem arises when the price for delivery is 100 times higher than
the existential deposit. In other words, when `ED * 100` does not cover
`BTT` + `BFPD`.

I check AHR/AHW/AHK/AHP and this problem has only AssetHubKusama
```
ED: 3333333
calculated price to parent delivery:  1031666634  (from xcm logs from the benchmark)
---

3333333 * 100 - BTT(3333333) - BFPD(1031666634) = −701666667
```
which results in the error;
```
2024-02-23 09:19:42 Unable to charge fee with error Module(ModuleError { index: 31, error: [17, 0, 0, 0], message: Some("FeesNotMet") })
Error: Input("Benchmark pallet_xcm::reserve_transfer_assets failed: FeesNotMet")
     
```

## Solution

The benchmarks `teleport_assets` and `reserve_transfer_assets` were
fixed by removing `ED * 100` and replacing it with `DeliveryHelper`
logic, which calculates the (almost real) price for delivery and sets it
along with the existential deposit as the initial balance for the
account used in the benchmark.


## TODO

- [ ] patch for 1.6 -
https://github.com/paritytech/polkadot-sdk/pull/3466
- [ ] patch for 1.7 -
https://github.com/paritytech/polkadot-sdk/pull/3465
- [ ] patch for 1.8 - TODO: PR

---------

Co-authored-by: Francisco Aguirre <franciscoaguirreperez@gmail.com>

polkadot/xcm/pallet-xcm-benchmarks/src/lib.rs

@@ -22,10 +22,8 @@ use codec::Encode;
 use frame_benchmarking::{account, BenchmarkError};
 use sp_std::prelude::*;
 use xcm::latest::prelude::*;
-use xcm_executor::{
-	traits::{ConvertLocation, FeeReason},
-	Config as XcmConfig, FeesMode,
-};
+use xcm_builder::EnsureDelivery;
+use xcm_executor::{traits::ConvertLocation, Config as XcmConfig};
 
 pub mod fungible;
 pub mod generic;
@@ -114,29 +112,3 @@ pub fn account_and_location<T: Config>(index: u32) -> (T::AccountId, Location) {
 
 	(account, location)
 }
-
-/// Trait for a type which ensures all requirements for successful delivery with XCM transport
-/// layers.
-pub trait EnsureDelivery {
-	/// Prepare all requirements for successful `XcmSender: SendXcm` passing (accounts, balances,
-	/// channels ...). Returns:
-	/// - possible `FeesMode` which is expected to be set to executor
-	/// - possible `Assets` which are expected to be subsume to the Holding Register
-	fn ensure_successful_delivery(
-		origin_ref: &Location,
-		dest: &Location,
-		fee_reason: FeeReason,
-	) -> (Option<FeesMode>, Option<Assets>);
-}
-
-/// `()` implementation does nothing which means no special requirements for environment.
-impl EnsureDelivery for () {
-	fn ensure_successful_delivery(
-		_origin_ref: &Location,
-		_dest: &Location,
-		_fee_reason: FeeReason,
-	) -> (Option<FeesMode>, Option<Assets>) {
-		// doing nothing
-		(None, None)
-	}
-}