Use span in StripFileExtension to speed up and use less memory (#13101)

(cherry picked from commit 475cea40a1)

tests/Umbraco.Tests.Benchmarks/StringFileExtensionBenchmark.cs

@@ -0,0 +1,80 @@
+using System;
+using BenchmarkDotNet.Attributes;
+using Umbraco.Tests.Benchmarks.Config;
+
+namespace Umbraco.Tests.Benchmarks
+{
+    [QuickRunWithMemoryDiagnoserConfig]
+    public class StringFileExtensionBenchmark
+    {
+        [Arguments("smallText.txt")]
+        [Arguments("aVeryLongTextThatContainsALotOfCharacters.txt")]
+        [Arguments("NotEvenAFile")]
+        [Benchmark(Baseline = true)]
+        public string StringStrip(string fileName)
+        {
+            // filenames cannot contain line breaks
+            if (fileName.Contains(Environment.NewLine) || fileName.Contains("\r") || fileName.Contains("\n"))
+            {
+                return fileName;
+            }
+
+            var lastIndex = fileName.LastIndexOf('.');
+            if (lastIndex > 0)
+            {
+                var ext = fileName.Substring(lastIndex);
+
+                // file extensions cannot contain whitespace
+                if (ext.Contains(" "))
+                {
+                    return fileName;
+                }
+
+                return string.Format("{0}", fileName.Substring(0, fileName.IndexOf(ext, StringComparison.Ordinal)));
+            }
+
+            return fileName;
+        }
+
+        [Arguments("smallText.txt")]
+        [Arguments("aVeryLongTextThatContainsALotOfCharacters.txt")]
+        [Arguments("NotEvenAFile")]
+        [Benchmark]
+        public string SpanStrip(string fileName)
+        {
+            // filenames cannot contain line breaks
+            if (fileName.Contains(Environment.NewLine) || fileName.Contains("\r") || fileName.Contains("\n"))
+            {
+                return fileName;
+            }
+
+            var spanFileName = fileName.AsSpan();
+            var lastIndex = spanFileName.LastIndexOf('.');
+            if (lastIndex > 0)
+            {
+                var ext = spanFileName[lastIndex..];
+
+                // file extensions cannot contain whitespace
+                if (ext.Contains(' '))
+                {
+                    return fileName;
+                }
+
+                return new string(spanFileName[..lastIndex]);
+            }
+
+            return fileName;
+        }
+    }
+
+    //|      Method |             fileName |      Mean |     Error |   StdDev | Ratio |  Gen 0 | Allocated |
+    //|------------ |--------------------- |----------:|----------:|---------:|------:|-------:|----------:|
+    //| StringStrip |         NotEvenAFile |  45.08 ns |  1.277 ns | 0.070 ns |  1.00 |      - |         - |
+    //|   SpanStrip |         NotEvenAFile |  45.13 ns |  6.131 ns | 0.336 ns |  1.00 |      - |         - |
+    //|             |                      |           |           |          |       |        |           |
+    //| StringStrip | aVery(...)s.txt[45] | 234.10 ns | 28.303 ns | 1.551 ns |  1.00 | 0.0751 |     240 B |
+    //|   SpanStrip | aVery(...)s.txt[45] |  98.37 ns | 14.839 ns | 0.813 ns |  0.42 | 0.0331 |     104 B |
+    //|             |                      |           |           |          |       |        |           |
+    //| StringStrip |        smallText.txt | 187.79 ns | 35.672 ns | 1.955 ns |  1.00 | 0.0348 |     112 B |
+    //|   SpanStrip |        smallText.txt |  62.46 ns | 13.795 ns | 0.756 ns |  0.33 | 0.0124 |      40 B |
+}