Move markerstack into its own object:

- owned by canvas
- pointed to by devices

Change-Id: Ia5abc60434cd34810ceea09ecab63c6b25eb972e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/283436
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Reed <reed@google.com>
6 files changed