Everything: Rich text redux (#5625)

* lord save me

* UI/ChatBox: Use the new `defStyle` param for `RenderMarkup`

The previous iteration didn't work because `AddMessage` can't inherit
its color from the PushColor (since we're not doing actual tag stacks
anymore).

* rebase touchup

Content.Server/Atmos/Components/GasTankComponent.cs

@@ -24,6 +24,7 @@ using Robust.Shared.Localization;
 using Robust.Shared.Player;
 using Robust.Shared.Serialization.Manager.Attributes;
 using Robust.Shared.Utility;
+using Robust.Shared.Utility.Markup;
 using Robust.Shared.ViewVariables;
 
 namespace Content.Server.Atmos.Components
@@ -108,7 +109,7 @@ namespace Content.Server.Atmos.Components
             UpdateUserInterface(true);
         }
 
-        public void Examine(FormattedMessage message, bool inDetailsRange)
+        public void Examine(FormattedMessage.Builder message, bool inDetailsRange)
         {
             message.AddMarkup(Loc.GetString("comp-gas-tank-examine", ("pressure", Math.Round(Air?.Pressure ?? 0))));
             if (IsConnected)