feat(perf-detector-threshold-configuration) Fixed dark mode styling a… (#52800)

- Dark mode styling off:
<img width="1038" alt="Screenshot 2023-07-13 at 11 02 29 AM"
src="https://github.com/getsentry/sentry/assets/60121741/ebc2419e-1085-4d33-92d2-6cfe619e0c32">

- Tooltip position off, needs to be closer to the slider track:
<img width="954" alt="Screenshot 2023-07-13 at 11 04 32 AM"
src="https://github.com/getsentry/sentry/assets/60121741/7ebd314f-6ac8-4e3d-8dd9-532363073e6e">

Co-authored-by: Abdullah Khan <abdullahkhan@PG9Y57YDXQ.local>

static/app/components/slider/index.tsx

@@ -209,7 +209,7 @@ function BaseSlider(
       skipWrapper
       isHoverable
       position="bottom"
-      offset={8}
+      offset={-15}
     >
       <SliderGroup {...groupProps} className={className}>
         {label && (

static/app/views/settings/projectPerformance/projectPerformance.tsx

@@ -914,7 +914,7 @@ const StyledJsonForm = styled(JsonForm)`
 `;
 
 const StyledPanelFooter = styled(PanelFooter)`
-  background: ${p => p.theme.white};
+  background: ${p => p.theme.background};
   border: 1px solid ${p => p.theme.border};
   border-radius: 0 0 calc(${p => p.theme.panelBorderRadius} - 1px)
     calc(${p => p.theme.panelBorderRadius} - 1px);