Revert "Have GrVkRenderTarget only use GrVkAttachments and not derive from GrVkImage."

This reverts commit 3dc6c190dabbe424345f3a8220be87bb92cdaf05.

Reason for revert: hitting assert about RT having input attachment on mali bots

Original change's description:
> Have GrVkRenderTarget only use GrVkAttachments and not derive from GrVkImage.
>
> This change moves the color and resolve attachments used in a
> GrVkRenderTarget to be a GrVkAttachment. These along with the msaa
> attachment now mean that GrVkRenderTarget no longer needs to derive from
> a GrVkImage.
>
> There are a couple ugly things in this CL since GrVkTexture still is a
> GrVkImage since we can't share attachments between GrVkRT and GrVkTex.
> But when that gets updated in the follow on CL things will look much nicer.
>
> Bug: skia:10727
> Change-Id: I2f12674d7517c6d6dea389e2d1fb7296028bcc85
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/379576
> Reviewed-by: Brian Salomon <bsalomon@google.com>
> Commit-Queue: Greg Daniel <egdaniel@google.com>

TBR=egdaniel@google.com,jvanverth@google.com,bsalomon@google.com

Change-Id: Ic46f3947ed9f7b2ca26e8418d643e7f89b6108d2
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:10727
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/380459
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
diff --git a/tests/BackendAllocationTest.cpp b/tests/BackendAllocationTest.cpp
index 7157989..577496d 100644
--- a/tests/BackendAllocationTest.cpp
+++ b/tests/BackendAllocationTest.cpp
@@ -78,18 +78,7 @@
             ERRORF(reporter, "Couldn't make SkSurface from backendTexture for %s\n",
                    ToolUtils::colortype_name(skColorType));
         } else {
-            // As we transition to using attachments instead of GrTextures and GrRenderTargets
-            // individual proxy instansiations may add multiple things to the cache. There would be
-            // an entry for the GrTexture/GrRenderTarget and entries for one or more attachments.
-            int cacheEntriesPerProxy = 1;
-            // We currently only have attachments on the vulkan backend
-            if (dContext->backend() == GrBackend::kVulkan) {
-                // If we ever make a rt with multisamples this would have an additional
-                // attachment as well.
-                cacheEntriesPerProxy++;
-            }
-            REPORTER_ASSERT(reporter,
-                            initialCount + cacheEntriesPerProxy == cache->getResourceCount());
+            REPORTER_ASSERT(reporter, initialCount+1 == cache->getResourceCount());
         }
     }