dotnet test test-adapter-path should be collection of DirectoryPath instead of single DirectoryPath

### Prerequisites

- [X] I have written a descriptive issue title
- [X] I have searched [issues](https://github.com/cake-build/cake/issues) to ensure it has not already been reported

### Cake runner

Cake .NET Tool, Cake Frosting

### Cake version

2.1

### Operating system

Linux, Windows, macOS

### Operating system architecture

64-Bit

### CI Server

_No response_

### What are you seeing?

https://cakebuild.net/api/Cake.Common.Tools.DotNet.Test/DotNetTestSettings/AA9D5613

```cs
public DirectoryPath TestAdapterPath { get; set; }
```

### What is expected?

```cs
public DirectoryPath[] TestAdapterPath { get; set; }
```

### Steps to Reproduce

it seems that dotnet test can use multiple test adapters

### Output log

_No response_

Start from the DotNetTestSettings.TestAdapterPath property and trace how Cake passes it to dotnet test. Check the existing tests or API usage for this setting, then verify that multiple adapter paths are accepted and documented consistently.

Written by the indexing model from the issue text.