Sort "deps" and "public_deps" when running the "gn format" command.

The "deps" and "public_deps" are sorted using the following rules:
  1. relative targets (":a", "../b") sort before absolute targets ("//c"),
  2. each group (relative and absolute) is sorted alphabetically.

BUG=554928

Review URL: https://codereview.chromium.org/1442023002

Cr-Original-Commit-Position: refs/heads/master@{#360042}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 354261e7dd491e88fde3b3bd3fa5ef6f1c629f00
10 files changed
tree: 64bb04579f4cab903b8a9073f5b3a79b10e03bed
  1. tools/