Adopt Compound Colours (#1086)

* Delete deprecated font tokens.

* Migrate from primaryContent to textPrimary/iconPrimary.

* Migrate from links to textLinkExternal.

* Migrate from secondaryContent to textSecondary/iconSecondary.

* Migrate from accent to textActionPrimary.

- Some uses changed to textPrimary or iconPrimary as necessary.
- Some manual tints removed now that that Sentry is fixed.

* Migrate alert to textCriticalPrimary/iconCriticalPrimary.

* Migrate from brand to textActionAccent/iconAccentTertiary.

* Migrate from background to bgCanvasDefault or text/iconOnSolidPrimary

* Migrate system to bgSubtleSecondary.

* Remove ElementUIColors and obsolete migrated colours.

* Migrate tertiaryContent/quaternaryContent/quinaryContent to Compound.

* Migrate bubblesYou/bubblesNotYou to use Compound.

* Update Compound.

DesignKit/Sources/Buttons/ElementCapsuleButtonStyle.swift

@@ -47,15 +47,15 @@ public struct ElementCapsuleButtonStyle: ButtonStyle {
     var background: some View {
         if isProminent {
             Capsule()
-                .foregroundColor(Color.element.accent)
+                .foregroundColor(Color.compound.textActionPrimary)
         } else {
             Capsule()
-                .stroke(Color.element.accent)
+                .stroke(Color.compound.textActionPrimary)
         }
     }
     
     var fontColor: Color {
-        isProminent ? .element.systemPrimaryBackground : .element.systemPrimaryLabel
+        isProminent ? .compound.textOnSolidPrimary : .compound.textPrimary
     }
 }