perf(#41392): improve cache busting inject performance (#41443)

The PR continues from #41392.

In #41392 the `dev ? cache-busting : empty` is executed per stylesheet instead of per page rendering. Since rendering link tags would be a hot path at the server, it might have accidentally introduced a performance overhead. The PR fixes that.

Note, this change also makes `Date.now()` only execute once instead of per stylesheets, however, this will most likely not cause any issues.

packages/next/server/app-render.tsx

@@ -1165,6 +1165,10 @@ export async function renderToHTMLOrFlight(
         Component: () => {
           let props = {}
 
+          // Add extra cache busting (DEV only) for https://github.com/vercel/next.js/issues/5860
+          // See also https://bugs.webkit.org/show_bug.cgi?id=187726
+          const cacheBustingUrlSuffix = dev ? `?ts=${Date.now()}` : ''
+
           return (
             <>
               {preloadedFontFiles.map((fontFile) => {
@@ -1184,9 +1188,7 @@ export async function renderToHTMLOrFlight(
                 ? stylesheets.map((href) => (
                     <link
                       rel="stylesheet"
-                      // Add extra cache busting (DEV only) for https://github.com/vercel/next.js/issues/5860
-                      // See also https://bugs.webkit.org/show_bug.cgi?id=187726
-                      href={`/_next/${href}${dev ? `?ts=${Date.now()}` : ''}`}
+                      href={`/_next/${href}${cacheBustingUrlSuffix}`}
                       // `Precedence` is an opt-in signal for React to handle
                       // resource loading and deduplication, etc:
                       // https://github.com/facebook/react/pull/25060