Implement InMemory Transport Layer for StellaOps Router

- Added InMemoryTransportOptions class for configuration settings including timeouts and latency.
- Developed InMemoryTransportServer class to handle connections, frame processing, and event management.
- Created ServiceCollectionExtensions for easy registration of InMemory transport services.
- Established project structure and dependencies for InMemory transport library.
- Implemented comprehensive unit tests for endpoint discovery, connection management, request/response flow, and streaming capabilities.
- Ensured proper handling of cancellation, heartbeat, and hello frames within the transport layer.

src/__Libraries/StellaOps.Microservice/IHeaderCollection.cs

@@ -0,0 +1,36 @@
+namespace StellaOps.Microservice;
+
+/// <summary>
+/// Abstraction for HTTP-style header collection.
+/// </summary>
+public interface IHeaderCollection : IEnumerable<KeyValuePair<string, string>>
+{
+    /// <summary>
+    /// Gets a header value by key.
+    /// </summary>
+    /// <param name="key">The header key (case-insensitive).</param>
+    /// <returns>The header value, or null if not found.</returns>
+    string? this[string key] { get; }
+
+    /// <summary>
+    /// Gets all values for a header key.
+    /// </summary>
+    /// <param name="key">The header key (case-insensitive).</param>
+    /// <returns>All values for the key.</returns>
+    IEnumerable<string> GetValues(string key);
+
+    /// <summary>
+    /// Tries to get a header value.
+    /// </summary>
+    /// <param name="key">The header key.</param>
+    /// <param name="value">The header value if found.</param>
+    /// <returns>True if the header was found.</returns>
+    bool TryGetValue(string key, out string? value);
+
+    /// <summary>
+    /// Checks if a header exists.
+    /// </summary>
+    /// <param name="key">The header key.</param>
+    /// <returns>True if the header exists.</returns>
+    bool ContainsKey(string key);
+}