SplitSettings: Show OS settings sidenav menu by default on large screens

This ports a browser settings CL to do the same:
https://chromium-review.googlesource.com/c/chromium/src/+/1583120

It also ports a fix for focus ring padding on the settings menu button:
https://chromium-review.googlesource.com/c/chromium/src/+/1611139

The tests are not ported yet because we're still setting up our test
scaffolding for the OS settings pages: crbug.com/955731

Bug: 628247,950007
Change-Id: I9941ae06532bc1088beaffa1f8dcc82a7d81e800
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1627241
Commit-Queue: James Cook <jamescook@chromium.org>
Auto-Submit: James Cook <jamescook@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#663104}
3 files changed