Create an abstract GrStrokeTessellator class

Now there is only one op to tessellate a stroke, and it creates its
own GrStrokeIndirectTessellator or GrStrokeHardwareTessellator
internally. This will allow us to dynamically switch into hardware
tessellation when we need to batch strokes that have different
parameters or colors.

Bug: chromium:1172543
Bug: skia:10419
Change-Id: I3cddb855fdbb9ab018785584497c843e3e31b75e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/366056
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
14 files changed