Reland "Added AutoreleasePool for managing pool memory in testing apps."

This is a reland of a36e089065d3cb4d8af7a12927d55d376a6f65e7

This is only active when Metal is enabled.

Original change's description:
> Added AutoreleasePool for managing pool memory in testing apps.
>
> This is only active on MacOS and iOS -- on other platforms it
> will do nothing as they have no need for autorelease pools.
>
> Bug: skia:8243
> Change-Id: Ib74968dab6e3455a72e726429832101d0d410076
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/217126
> Commit-Queue: Jim Van Verth <jvanverth@google.com>
> Reviewed-by: Brian Osman <brianosman@google.com>

Bug: skia:8243
Change-Id: I743a3dcc93b46387a6a330e855c2e8810b482544
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/217379
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
diff --git a/public.bzl b/public.bzl
index 3c4ae7e..2b52e15 100644
--- a/public.bzl
+++ b/public.bzl
@@ -457,6 +457,7 @@
         "tests/*.cpp",
         "tests/*.h",
         "tools/ios_utils.h",
+        "tools/AutoreleasePool.h",
         "tools/BinaryAsset.h",
         "tools/BigPathBench.inc",
         "tools/CrashHandler.cpp",