Improve depend-info --dot output

[dg0yt]

Make test format more readable for humans with line breaks. (Note: https://learn.microsoft.com/en-us/vcpkg/commands/depend-info#dot doesn't show literal output.)
Use pristine package names via quotes.
Use "Sans" font.

Output for ableton-link:

digraph G{ rankdir=LR; node [fontname=Sans]; edge [minlen=3]; overlap=false;
"ableton";
"ableton" -> "ableton-link";
"ableton-link";
"ableton-link" -> "asio";
"ableton-link" -> "vcpkg-cmake";
"ableton-link" -> "vcpkg-cmake-config";
"asio";
"asio" -> "vcpkg-cmake";
"asio" -> "vcpkg-cmake-config";
"vcpkg-cmake";
"vcpkg-cmake-config";
"2 singletons...";
}

Wish list:

• Drop the "singletons" comment node.
• Top-bottom rankdir, which is the default format for dot, also for mermaid.
  (Users can override it with dot -Grankdir=TB.) Output:
  

[BillyONeal]

Thanks for the improvement!