[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>

substrate/frame/support/src/traits/members.rs

@@ -137,6 +137,14 @@ impl<A, B, These: ContainsPair<A, B>, Those: ContainsPair<A, B>> ContainsPair<A,
 	}
 }
 
+/// An implementation of [`Contains`] which contains only equal members to `T`.
+pub struct Equals<T>(PhantomData<T>);
+impl<X: PartialEq, T: super::Get<X>> Contains<X> for Equals<T> {
+	fn contains(t: &X) -> bool {
+		t == &T::get()
+	}
+}
+
 /// Create a type which implements the `Contains` trait for a particular type with syntax similar
 /// to `matches!`.
 #[macro_export]