Fix Satellite Assembly loading (dotnet/coreclr#24191)

* Fix Satellite Assembly loading

When loading satellite assemblies, we should probe next to the parent
assembly and load into the same AssemblyLoadContext as the parent
assembly.

Disable fallback probing for satellite assemblies.

Add AssemblyLoadContext.Resolving handler to probe for satellite
assemblies next to parent

Fixes mono#20979

* Call ResolveSatelliteAssembly from native

Only call ResolveSatelliteAssembly from native when
resolving a satellite assembly

* PR Feedback

Minimize string creation
Remove unnecessary if null checks
Eliminate corner cases by only allowing one case insensitive matching directory.

* ResolveSatelliteAssembly should ...

ResolveSatelliteAssembly should always be called on the ALC which loaded parentAssembly

Simplify code.
Add Debug.Assert

* Remove case insensitive culture search

* PR Feedback

* Fix parentAssembly logic

* Fixes from initial testing

* Add probe for lower case culture name

* PR feedback

Signed-off-by: dotnet-bot <dotnet-bot@microsoft.com>

Author: sdmaclea

netcore/System.Private.CoreLib/shared/System/Runtime/Loader/AssemblyLoadContext.cs

@@ -187,7 +187,7 @@ public event Func<Assembly, string, IntPtr> ResolvingUnmanagedDll
         //
         // Inputs: The AssemblyLoadContext and AssemblyName to be loaded
         // Returns: The Loaded assembly object.
-        public event Func<AssemblyLoadContext, AssemblyName, Assembly> Resolving
+        public event Func<AssemblyLoadContext, AssemblyName, Assembly?> Resolving
         {
             add
             {
@@ -555,6 +555,43 @@ public void Dispose()
                 }
             }
         }
+
+        private Assembly? ResolveSatelliteAssembly(AssemblyName assemblyName)
+        {
+            // Called by native runtime when CultureName is not empty
+            Debug.Assert(assemblyName.CultureName?.Length > 0);
+
+            string satelliteSuffix = ".resources";
+
+            if (assemblyName.Name == null || !assemblyName.Name.EndsWith(satelliteSuffix, StringComparison.Ordinal))
+                return null;
+
+            string parentAssemblyName = assemblyName.Name.Substring(0, assemblyName.Name.Length - satelliteSuffix.Length);
+
+            Assembly parentAssembly = LoadFromAssemblyName(new AssemblyName(parentAssemblyName));
+
+            AssemblyLoadContext parentALC = GetLoadContext(parentAssembly)!;
+
+            string parentDirectory = Path.GetDirectoryName(parentAssembly.Location)!;
+
+            string assemblyPath = Path.Combine(parentDirectory, assemblyName.CultureName!, $"{assemblyName.Name}.dll");
+
+            if (Internal.IO.File.InternalExists(assemblyPath))
+            {
+                return parentALC.LoadFromAssemblyPath(assemblyPath);
+            }
+            else if (Path.IsCaseSensitive)
+            {
+                assemblyPath = Path.Combine(parentDirectory, assemblyName.CultureName!.ToLowerInvariant(), $"{assemblyName.Name}.dll");
+
+                if (Internal.IO.File.InternalExists(assemblyPath))
+                {
+                    return parentALC.LoadFromAssemblyPath(assemblyPath);
+                }
+            }
+
+            return null;
+        }
     }
 
     internal sealed class DefaultAssemblyLoadContext : AssemblyLoadContext