AsyncCollectionRequestMessage<T> creates a CancellationTokenSource that never gets disposed

### Describe the bug

I was examining the code for the the [AsyncCollectionRequestMessage](https://github.com/CommunityToolkit/dotnet/blob/main/src/CommunityToolkit.Mvvm/Messaging/Messages/AsyncCollectionRequestMessage%7BT%7D.cs) class and I noticed it creates a private `CancellationTokenSource` that never gets Dispose() called on it.

I looked at `CancellationTokenSource`'s dispose methods and it's non-trivial, potentially disposing of a `System.ITimer` and a `ManualResetEvent` - both things that are potentially finite resources, so better to release ASAP.

### Regression

_No response_

### Steps to reproduce

No reproduction, just observation of the code.

### Expected behavior

There should be an opportunity to dispose the CancellationTokenSource. Most obvious possible way would be to make thing that comes to mind would be make `AsyncCollectionRequestMessage` implement `IDispose` so that users could call it.

### Screenshots

_No response_

### IDE and version

VS 2022

### IDE version

17.14.11

### Nuget packages

- [ ] CommunityToolkit.Common
- [ ] CommunityToolkit.Diagnostics
- [ ] CommunityToolkit.HighPerformance
- [x] CommunityToolkit.Mvvm (aka MVVM Toolkit)

### Nuget package version(s)

8.4.0

### Additional context

_No response_

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