Add implementation for SweepLine

Add an implementation for a sweep line with unit tests. Integrate
the sweep line and the event queue into a working Bentley Ottmann
crossing finder.

Bug: b/297220808

Change-Id: I793ad18804c3524b543d24300e9993d72d3559ed
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/750076
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Herb Derby <herb@google.com>
10 files changed