Add support for Dependency Injection with ITextEmbeddingGenerator (#503)

## Motivation and Context (Why the change? What's the scenario?)

Add support for Dependency Injection with ITextEmbeddingGenerator

See #334. This PR
replaces #444 so that it
excludes unnecessary changes.

Author: marcominerva

service/Abstractions/KernelMemoryBuilderExtensions.cs

@@ -137,6 +137,13 @@ public static IKernelMemoryBuilder WithCustomEmbeddingGenerator(
         return builder;
     }
 
+    public static IKernelMemoryBuilder WithCustomEmbeddingGenerator<T>(
+           this IKernelMemoryBuilder builder) where T : class, ITextEmbeddingGenerator
+    {
+        builder.AddSingleton<ITextEmbeddingGenerator, T>();
+        return builder;
+    }
+
     public static IKernelMemoryBuilder WithCustomMemoryDb(
         this IKernelMemoryBuilder builder,
         IMemoryDb service,