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.

ElementX/Sources/Other/SwiftUI/Views/LoadableAvatarImage.swift

@@ -38,7 +38,7 @@ struct LoadableAvatarImage: View {
     var body: some View {
         avatar
             .frame(width: frameSize, height: frameSize)
-            .background(Color.element.background)
+            .background(Color.compound.bgCanvasDefault)
             .clipShape(Circle())
     }