[skottie] Make animated image support generally available

Consolidate some helpers under skottie_utils, and update all related
tools to support animated images.

TBR=
Change-Id: If08e97143a11d9a414f3230a49ab4284c508b9d0
Reviewed-on: https://skia-review.googlesource.com/c/169342
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>
diff --git a/BUILD.gn b/BUILD.gn
index c889c8b..f23716b 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -1705,6 +1705,7 @@
         ":tests",
         ":tool_utils",
         "modules/skottie",
+        "modules/skottie:utils",
         "modules/sksg",
         "//third_party/jsoncpp",
         "//third_party/libpng",
@@ -2146,6 +2147,7 @@
       ":skia",
       ":tool_utils",
       "modules/skottie",
+      "modules/skottie:utils",
       "modules/sksg",
       "modules/sksg:samples",
       "//third_party/imgui",