Split SkYUVAInfo::PlanarConfig into PlaneConfig and Subsampling enums

Sometimes it's helpful to think about subsampling separately from
how the channels are spread across planes.

Bug: skia:10632
Change-Id: Ib03f71195f9706ef6def418b1f2125c29e0cf738
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/334102
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
diff --git a/RELEASE_NOTES.txt b/RELEASE_NOTES.txt
index 59b06d5..848f86c 100644
--- a/RELEASE_NOTES.txt
+++ b/RELEASE_NOTES.txt
@@ -7,6 +7,10 @@
 Milestone 88
 ------------
 
+  * SkYUVAInfo now has separate enums for division of channels among planes and
+    the subsampling. The previous combined enum, PlanarConfig, is deprecated.
+    https://review.skia.org/334102
+
   * Simplified SkDeferredDisplayListRecorder promise image API. Removed "release"
     callback and renamed "done" callback to "release". The new "release" proc can
     be null. Added a new SkYUVAInfo-based factory for YUVA promise texture images