Bentley-Ottmann EventQueue

This is not really the EventQueue, but all the
infrastructure to get the module up and running.

I added empty source files because bazel can't abide
a module without sources.

Change-Id: Iab6e96d16979b23db7b19f2cc9fc62b957259290
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/737179
Reviewed-by: Kevin Lubick <kjlubick@google.com>
Commit-Queue: Herb Derby <herb@google.com>
11 files changed