Add row and column accessors for tables and grids

src/Spectre.Console/Internal/Collections/ListWithCallback.cs

@@ -4,7 +4,7 @@ using System.Collections.Generic;
 
 namespace Spectre.Console.Internal.Collections
 {
-    internal sealed class ListWithCallback<T> : IList<T>
+    internal sealed class ListWithCallback<T> : IList<T>, IReadOnlyList<T>
     {
         private readonly List<T> _list;
         private readonly Action _callback;

src/Spectre.Console/Internal/Extensions/EnumerableExtensions.cs

@@ -6,6 +6,21 @@ namespace Spectre.Console.Internal
 {
     internal static class EnumerableExtensions
     {
+        public static int GetCount<T>(this IEnumerable<T> source)
+        {
+            if (source is IList<T> list)
+            {
+                return list.Count;
+            }
+
+            if (source is T[] array)
+            {
+                return array.Length;
+            }
+
+            return source.Count();
+        }
+
         public static void ForEach<T>(this IEnumerable<T> source, Action<T> action)
         {
             foreach (var item in source)