Revert to case insenstive by default to avoid breaking changes.

src/Microsoft.Performance.SDK.Runtime/Discovery/AssemblyExtensionDiscovery.cs

@@ -138,7 +138,7 @@ namespace Microsoft.Performance.SDK.Runtime.Discovery
         /// </returns>
         public bool ProcessAssemblies(IEnumerable<string> directoryPaths, out ErrorInfo error)
         {
-            return this.ProcessAssemblies(directoryPaths, true, null, null, MatchCasing.PlatformDefault, out error);
+            return this.ProcessAssemblies(directoryPaths, true, null, null, MatchCasing.CaseInsensitive, out error);
         }
 
         /// <summary>

src/Microsoft.Performance.Toolkit.Engine/AssemblyDiscoverySettings.cs

@@ -35,7 +35,7 @@ namespace Microsoft.Performance.Toolkit.Engine
         public AssemblyDiscoverySettings(
             bool includeSubdirectories,
             IEnumerable<string> searchPatterns)
-            : this(includeSubdirectories, searchPatterns, null, MatchCasing.PlatformDefault)
+            : this(includeSubdirectories, searchPatterns, null, MatchCasing.CaseInsensitive)
         {
         }