[xcm] Small enhancements for NetworkExportTable and xcm-builder (#1848)

## Summary

This PR introduces several enhancements.

The current implementation of `NetworkExportTable` lacks remote location
filtering support beyond `NetworkId` lookup. To provide more control and
granularity, it's essential to allow configuration for bridging to
different consensus `NetworkId` while restricting access e.g. to
particular remote parachains.

Additionally, the `StartsWith` and `Equals` and
`StartsWithExplicitGlobalConsensus` helper functions, which are in
active use, are moved to the `xcm-builder` and `frame_support` modules
for better code organization.

Adds a new `LocationWithAssetFilters` filter to enable location-based
and asset-related filtering. This filter is useful for configuring the
`pallet_xcm` filter for
[XcmTeleportFilter](https://github.com/paritytech/polkadot-sdk/blob/master/polkadot/xcm/pallet-xcm/src/lib.rs#L212)
and
[XcmReserveTransferFilter](https://github.com/paritytech/polkadot-sdk/blob/master/polkadot/xcm/pallet-xcm/src/lib.rs#L216)
to restrict specific assets.

Furthermore, the `BridgeMessage` fields are not accessible outside of
`xcm-builder`, limiting the ability to create custom logic dependent on
it.

---------

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

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

@@ -0,0 +1,50 @@
+// Copyright (C) Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Polkadot is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Various implementations and utilities for matching and filtering `MultiLocation` and
+//! `InteriorMultiLocation` types.
+
+use frame_support::traits::{Contains, Get};
+use xcm::latest::{InteriorMultiLocation, MultiLocation, NetworkId};
+
+/// An implementation of `Contains` that checks for `MultiLocation` or
+/// `InteriorMultiLocation` if starts with the provided type `T`.
+pub struct StartsWith<T>(sp_std::marker::PhantomData<T>);
+impl<T: Get<MultiLocation>> Contains<MultiLocation> for StartsWith<T> {
+	fn contains(t: &MultiLocation) -> bool {
+		t.starts_with(&T::get())
+	}
+}
+impl<T: Get<InteriorMultiLocation>> Contains<InteriorMultiLocation> for StartsWith<T> {
+	fn contains(t: &InteriorMultiLocation) -> bool {
+		t.starts_with(&T::get())
+	}
+}
+
+/// An implementation of `Contains` that checks for `MultiLocation` or
+/// `InteriorMultiLocation` if starts with expected `GlobalConsensus(NetworkId)` provided as type
+/// `T`.
+pub struct StartsWithExplicitGlobalConsensus<T>(sp_std::marker::PhantomData<T>);
+impl<T: Get<NetworkId>> Contains<MultiLocation> for StartsWithExplicitGlobalConsensus<T> {
+	fn contains(location: &MultiLocation) -> bool {
+		matches!(location.interior.global_consensus(), Ok(requested_network) if requested_network.eq(&T::get()))
+	}
+}
+impl<T: Get<NetworkId>> Contains<InteriorMultiLocation> for StartsWithExplicitGlobalConsensus<T> {
+	fn contains(location: &InteriorMultiLocation) -> bool {
+		matches!(location.global_consensus(), Ok(requested_network) if requested_network.eq(&T::get()))
+	}
+}