[API Proposal]: Add support for X-Wing

### Background and motivation

Migrating from X25119 to [X-Wing hybrid post-quantum KEM](https://datatracker.ietf.org/doc/draft-connolly-cfrg-xwing-kem/) is a logical step for security conscious projects. Since [MLKem](https://learn.microsoft.com/en-us/dotnet/api/system.security.cryptography.mlkem?view=net-11.0) and [X25519](https://learn.microsoft.com/en-us/dotnet/api/system.security.cryptography.x25519diffiehellman?view=net-11.0) are part of the framework, everything is given to implement the API for X-Wing. Also it would support the adaptation of X-Wing.

### API Proposal

```csharp
namespace System.Security.Cryptography;

public static class XWing
{
public const int DecapsulationKeySizeInBytes = 32;
public const int EncapsulationKeySizeInBytes = 1216;
public const int CiphertextSizeInBytes = 1120;
public const int SharedSecretSizeInBytes = 32;

public static bool IsSupported { get; }

public static (byte[] DecapsulationKey, byte[] EncapsulationKey) GenerateKeyPair();

public static (byte[] SharedSecret, byte[] Ciphertext) Encapsulate(ReadOnlySpan encapsulationKey)

public static byte[] Decapsulate(ReadOnlySpan ciphertext, ReadOnlySpan decapsulationKey)
}
```

### API Usage

```csharp
// Step 1
(byte[] DecapsulationKey, byte[] EncapsulationKey) = XWing.GenerateKeyPair();

// Step 2
(byte[] EncapsulatedSecret, byte[] Ciphertext) = XWing.Encapsulate(EncapsulationKey);

// Step 3
byte[] decapsulatedSecret = XWing.Decapsulate(Ciphertext, DecapsulationKey);
```

### Alternative Designs

_No response_

### Risks

_No response_

Start by reviewing the proposed XWing API alongside the existing MLKem and X25519 framework APIs. Determine the implementation and validation work needed for key generation, encapsulation, and decapsulation; done means the framework exposes the proposed API with interoperable X-Wing support.

Written by the indexing model from the issue text.