Make the backtrace configuration UI match other booleans

This has the side benefit of not exceeding the width of the config
widget.

Author: shepmaster

tests/spec/features/backtrace_spec.rb

@@ -12,7 +12,7 @@
 
   context "backtraces are enabled" do
     before do
-      in_advanced_options_menu { choose 'enabled' }
+      in_advanced_options_menu { within(:config_option, 'Backtrace') { choose 'On' } }
       within(:header) { click_on("Run") }
     end
 

tests/spec/spec_helper.rb

@@ -88,6 +88,12 @@
   css { '[data-test-id = "notification"]' }
 end
 
+Capybara.add_selector(:config_option) do
+  xpath do |label|
+    ".//div[span[contains(., '#{label}')]]"
+  end
+end
+
 RSpec.configure do |config|
   config.after(:example, :js) do
     page.execute_script <<~JS

ui/frontend/AdvancedOptionsMenu.tsx

@@ -38,8 +38,10 @@ const AdvancedOptionsMenu: React.FC = () => {
       <EitherConfig
         id="backtrace"
         name="Backtrace"
-        a={Backtrace.Disabled}
-        b={Backtrace.Enabled}
+        a={Backtrace.Enabled}
+        b={Backtrace.Disabled}
+        aLabel="On"
+        bLabel="Off"
         value={backtrace}
         isDefault={isBacktraceDefault}
         onChange={changeBacktrace}