Fix some friend access violations by allowing others access. (#8594)

Rename Friend attribute to Access attribute.
Updates submodule to v0.21.0.0 as well.

Content.Server/Chemistry/Components/SolutionManager/SolutionContainerManagerComponent.cs

@@ -4,11 +4,12 @@ using Content.Shared.Chemistry.Components;
 namespace Content.Server.Chemistry.Components.SolutionManager
 {
     [RegisterComponent]
-    [Friend(typeof(SolutionContainerSystem))]
+    [Access(typeof(SolutionContainerSystem))]
     public sealed class SolutionContainerManagerComponent : Component
     {
         [ViewVariables]
         [DataField("solutions")]
+        [Access(typeof(SolutionContainerSystem), Other = AccessPermissions.ReadExecute)] // FIXME Friends
         public readonly Dictionary<string, Solution> Solutions = new();
     }
 }