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/Power/Components/ApcComponent.cs

@@ -6,7 +6,7 @@ using Content.Shared.Sound;
 namespace Content.Server.Power.Components;
 
 [RegisterComponent]
-[Friend(typeof(ApcSystem))]
+[Access(typeof(ApcSystem))]
 public sealed class ApcComponent : BaseApcNetComponent
 {
     [DataField("onReceiveMessageSound")]

Content.Server/Power/Components/CableComponent.cs

@@ -9,7 +9,7 @@ namespace Content.Server.Power.Components
     ///     Allows the attached entity to be destroyed by a cutting tool, dropping a piece of cable.
     /// </summary>
     [RegisterComponent]
-    [Friend(typeof(CableSystem))]
+    [Access(typeof(CableSystem))]
     public sealed class CableComponent : Component
     {
         [DataField("cableDroppedOnCutPrototype", customTypeSerializer: typeof(PrototypeIdSerializer<EntityPrototype>))]

Content.Server/Power/Components/ExtensionCableProviderComponent.cs

@@ -3,7 +3,7 @@
 namespace Content.Server.Power.Components
 {
     [RegisterComponent]
-    [Friend(typeof(ExtensionCableSystem))]
+    [Access(typeof(ExtensionCableSystem))]
     public sealed class ExtensionCableProviderComponent : Component
     {
         /// <summary>

Content.Server/Power/Components/ExtensionCableReceiverComponent.cs

@@ -3,7 +3,7 @@
 namespace Content.Server.Power.Components
 {
     [RegisterComponent]
-    [Friend(typeof(ExtensionCableSystem))]
+    [Access(typeof(ExtensionCableSystem))]
     public sealed class ExtensionCableReceiverComponent : Component
     {
         [ViewVariables]