.NET: Performance improvements for VectorStoreTextSearch

- Fix CA1859: Use specific return types BinaryExpression? and MethodCallExpression?
  instead of generic Expression? for better performance
- Improve test model: Use IReadOnlyList<string> instead of string[] for Tags property
  to follow .NET collection best practices

These changes address code analyzer warnings and apply reviewer applicable feedback
from other PRs in the Issue #10456 modernization series.

Author: alzarei

dotnet/src/SemanticKernel.Core/Data/TextSearch/VectorStoreTextSearch.cs

@@ -580,7 +580,7 @@ private async IAsyncEnumerable<string> GetResultsAsStringAsync(IAsyncEnumerable<
     /// <param name="value">The value to compare against.</param>
     /// <param name="parameter">The parameter expression.</param>
     /// <returns>The body expression for equality, or null if not supported.</returns>
-    private static Expression? CreateEqualityBodyExpression(string fieldName, object value, ParameterExpression parameter)
+    private static BinaryExpression? CreateEqualityBodyExpression(string fieldName, object value, ParameterExpression parameter)
     {
         try
         {
@@ -682,7 +682,7 @@ private async IAsyncEnumerable<string> GetResultsAsStringAsync(IAsyncEnumerable<
     /// <param name="parameter">The parameter expression.</param>
     /// <returns>The body expression for collection contains, or null if not supported.</returns>
     [RequiresDynamicCode("Calls System.Reflection.MethodInfo.MakeGenericMethod(params Type[])")]
-    private static Expression? CreateAnyTagEqualToBodyExpression(string fieldName, string value, ParameterExpression parameter)
+    private static MethodCallExpression? CreateAnyTagEqualToBodyExpression(string fieldName, string value, ParameterExpression parameter)
     {
         try
         {

dotnet/src/SemanticKernel.UnitTests/Data/VectorStoreTextSearchTestBase.cs

@@ -249,7 +249,7 @@ public sealed class DataModelWithTags
         public required string Tag { get; init; }
 
         [VectorStoreData(IsIndexed = true)]
-        public required string[] Tags { get; init; }
+        public required IReadOnlyList<string> Tags { get; init; }
 
         [VectorStoreVector(1536)]
         public string? Embedding { get; init; }