Printing: Add metric for discovered printers setup

- This metric records the printer setup result when a user clicks the
  Setup button in OS Printer Settings.
- It will help for understanding how often Discovered printers need to
  be manually configured
- Add the previously missing values to the `PrinterSetupResult` enum

Change-Id: I8023ef20c6299b935f80b7278e61afe2cd129845
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4210125
Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Benjamin Gordon <bmgordon@chromium.org>
Commit-Queue: Gavin Williams <gavinwill@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1100613}