Implement User Survey UX (Desktop)

It appears that design and strings are finalised for the user survey.

• Figma: https://www.figma.com/design/4XiUaZPch3ejewlZO56lkR/Tor-Browser-14.5?node-id=748-19948&t=qma1hS80WCiABt2X-1
• Strings (ready for merge): #43489 (comment 3161955)
• We will gate this UX on a 2-week window (most likely from April 29th through May 13th (but still waiting on confirmation)
• Dismissing the dialog via the Not now and the 'close' button prevents it from ever being shown again, while the 'launch' button will open the survey but not affect the dialog's visibility
• Stable and Legacy only (gated at runtime, we will merge to both Alpha and Stable branches as the survey will run through the transition)

Let's plan on getting this in ASAP so we can be sure to hit the dates and to ensure strings get maximally translated.