Adopt the new start chat button design. (#4013)

* Update compound and handle plain to tertiary/textLink button style updates.

* Update the start chat button to use the right icon/style.

* Update preview snapshots.

* Fix remaining snapshots.

ElementX/Sources/Screens/AppLock/AppLockSetupPINScreen/View/AppLockSetupPINScreen.swift

@@ -39,7 +39,7 @@ struct AppLockSetupPINScreen: View {
                     Button(L10n.screenAppLockForgotPin) {
                         context.send(viewAction: .forgotPIN)
                     }
-                    .buttonStyle(.compound(.plain))
+                    .buttonStyle(.compound(.tertiary, size: .medium))
                 }
             }
             .padding(.horizontal, 16)