Add all classes to AssemblyLoadContext collection

To ensure that the initializer is called before any other code. This is
as close to a global init hook as I can find.

test/csharp/test_Binders.cs

@@ -4,6 +4,7 @@ using System.Management.Automation.Language;
 
 namespace PSTests
 {
+    [Collection("AssemblyLoadContext")]
     public static class PSEnumerableBinderTests
     {
         [Fact]

test/csharp/test_CorePsExtensions.cs

@@ -4,6 +4,7 @@ using System.Management.Automation;
 
 namespace PSTests
 {
+    [Collection("AssemblyLoadContext")]
     public static class CorePsExtensionsTests
     {
         [Fact]

test/csharp/test_CorePsPlatform.cs

@@ -6,6 +6,7 @@ using System.Management.Automation;
 
 namespace PSTests
 {
+    [Collection("AssemblyLoadContext")]
     public static class PlatformTests
     {
         [Fact]

test/csharp/test_ExtensionMethods.cs

@@ -4,6 +4,7 @@ using System.Management.Automation;
 
 namespace PSTests
 {
+    [Collection("AssemblyLoadContext")]
     public static class PSTypeExtensionsTests
     {
         [Fact]

test/csharp/test_FileSystemProvider.cs

@@ -5,6 +5,7 @@ using Microsoft.PowerShell.Commands;
 
 namespace PSTests
 {
+    [Collection("AssemblyLoadContext")]
     public static class FileSystemProviderTests
     {
         [Fact]

test/csharp/test_MshSnapinInfo.cs

@@ -5,6 +5,7 @@ using System.Management.Automation;
 namespace PSTests
 {
     // Not static because a test requires non-const variables
+    [Collection("AssemblyLoadContext")]
     public class MshSnapinInfoTests
     {
         // Test that it does not throw an exception

test/csharp/test_PSVersionInfo.cs

@@ -4,6 +4,7 @@ using System.Management.Automation;
 
 namespace PSTests
 {
+    [Collection("AssemblyLoadContext")]
     public static class PSVersionInfoTests
     {
         [Fact]

test/csharp/test_SecuritySupport.cs

@@ -4,6 +4,7 @@ using System.Management.Automation;
 
 namespace PSTests
 {
+    [Collection("AssemblyLoadContext")]
     public static class SecuritySupportTests
     {
         [Fact]

test/csharp/test_Utils.cs

@@ -4,6 +4,7 @@ using System.Management.Automation;
 
 namespace PSTests
 {
+    [Collection("AssemblyLoadContext")]
     public static class UtilsTests
     {
         [Fact]