Remove singleton instances from compare strategies

Eliminated the static singleton Instance properties from DefaultCompareStrategy and SemVerCompareStrategy. Updated StringVersion to instantiate new strategy objects directly instead of using the singleton, improving encapsulation and reducing shared state.

Author: emako

src/System.StringVersion/DefaultCompareStrategy.cs

@@ -5,11 +5,6 @@ namespace System.StringVersion;
 /// </summary>
 public class DefaultCompareStrategy : IVersionCompareStrategy
 {
-    /// <summary>
-    /// Singleton instance of the default compare strategy.
-    /// </summary>
-    public static DefaultCompareStrategy Instance { get; } = new DefaultCompareStrategy();
-
     /// <summary>
     /// Compares two arrays of version tokens using default rules.
     /// </summary>

src/System.StringVersion/SemVerCompareStrategy.cs

@@ -8,11 +8,6 @@ namespace System.StringVersion;
 /// </summary>
 public class SemVerCompareStrategy : IVersionCompareStrategy
 {
-    /// <summary>
-    /// Singleton instance of the SemVer compare strategy.
-    /// </summary>
-    public static SemVerCompareStrategy Instance { get; } = new SemVerCompareStrategy();
-
     /// <summary>
     /// Compares two arrays of version tokens using SemVer rules.
     /// </summary>

src/System.StringVersion/StringVersion.cs

@@ -57,7 +57,7 @@ public StringVersion(string? original)
         }
         Tokens = tokens;
         Original = original ?? string.Empty;
-        Strategy = SemVerCompareStrategy.Instance;
+        Strategy = new SemVerCompareStrategy();
     }
 
     /// <summary>
@@ -72,7 +72,7 @@ public StringVersion(VersionToken[] tokens, string? original, IVersionCompareStr
         // Null checks to guarantee no exception is thrown
         Tokens = tokens ?? [];
         Original = original ?? string.Empty;
-        Strategy = strategy ?? SemVerCompareStrategy.Instance;
+        Strategy = strategy ?? new SemVerCompareStrategy();
     }
 
     /// <summary>