Count cycles in Android package dependency graphs

A new script has been added to count and optionally output cycles in
package graphs. A limit to cycle size must be supplied, ideally around 5
or 6 to keep the script runtime low since the number of cycles is
exponential.

For more detailed usage, see `./count_cycles.py -h`.

Bug: 1106484
Change-Id: I01923eaab24eb3c6641a23039c80f60a0bc0e212
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2303054
Commit-Queue: James Long <yjlong@google.com>
Reviewed-by: Samuel Huang <huangs@chromium.org>
Reviewed-by: Mohamed Heikal <mheikal@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#791996}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: a0465fa219b92da2d0302f4e63ef5056f12102b6
3 files changed