feat: Add unit tests and fakes for Crestron environment and data store

- Introduced `FakeCrestronEnvironment` and `FakeEthernetHelper` for testing purposes.
- Implemented `InMemoryCrestronDataStore` to facilitate unit tests for data storage.
- Created `DebugServiceTests` to validate the behavior of debug-related services.
- Added project files for unit tests targeting .NET 9.0 with necessary dependencies.
- Developed production adapters (`CrestronConsoleAdapter`, `CrestronDataStoreAdapter`, `CrestronEnvironmentAdapter`, `CrestronEthernetAdapter`) to interface with the Crestron SDK.
- Updated `Debug` class to utilize injected service abstractions instead of direct SDK calls.
- Enhanced `ControlSystem` initialization to register service adapters before usage.

src/PepperDash.Core.Abstractions/ICrestronEnvironment.cs

@@ -0,0 +1,45 @@
+namespace PepperDash.Core.Abstractions;
+
+/// <summary>
+/// Abstracts <c>Crestron.SimplSharp.CrestronEnvironment</c> to allow unit testing
+/// without the Crestron SDK.
+/// </summary>
+public interface ICrestronEnvironment
+{
+    /// <summary>Gets the platform the program is executing on.</summary>
+    DevicePlatform DevicePlatform { get; }
+
+    /// <summary>Gets the current runtime environment.</summary>
+    RuntimeEnvironment RuntimeEnvironment { get; }
+
+    /// <summary>Gets the platform-appropriate newline string.</summary>
+    string NewLine { get; }
+
+    /// <summary>Gets the application number (program slot).</summary>
+    uint ApplicationNumber { get; }
+
+    /// <summary>Gets the room ID (used in Crestron Virtual Control / server environments).</summary>
+    uint RoomId { get; }
+
+    /// <summary>Raised when program status changes (starting, stopping, etc.).</summary>
+    event EventHandler<ProgramStatusEventArgs> ProgramStatusChanged;
+
+    /// <summary>Raised when the ethernet link changes state.</summary>
+    event EventHandler<PepperDashEthernetEventArgs> EthernetEventReceived;
+
+    /// <summary>Gets the application root directory path.</summary>
+    string GetApplicationRootDirectory();
+}
+
+/// <summary>
+/// Event args for <see cref="ICrestronEnvironment.ProgramStatusChanged"/>.
+/// </summary>
+public class ProgramStatusEventArgs : EventArgs
+{
+    public ProgramStatusEventType EventType { get; }
+
+    public ProgramStatusEventArgs(ProgramStatusEventType eventType)
+    {
+        EventType = eventType;
+    }
+}