Rename some AtlasTypes for clarity.

DrawToken has been renamed to AtlasToken, since it is used for flushes
and draws, and some of the internals of TokenTracker have been renamed
to make it more consistent.

Bug: b/246953695
Change-Id: I0557d71ceace4ebc039d3f0a2e2836e0bb1d142b
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/620225
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
20 files changed