Add brute force crossing detection

This is used for testing the sweepline algorithm in
a future CL. A very simple O(N^2) algorithm for finding
crossings.

The paper is here:
https://drive.google.com/file/d/1lYw5m8ryC5C1DiG1NIHOV5tp4U4GdgH2/view?usp=drive_link

To see how this change fits in to future CLs consult:
https://skia-review.googlesource.com/c/skia/+/784551

Bug: b/297220808
Change-Id: I1e99c00bf9c3d5cbfa376403a7fc5a0afaaf769d
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/798396
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Reviewed-by: Jim Van Verth <jvanverth@google.com>
3 files changed