Reland "Redesign program key construction"

This is a reland of bbbf1a7f50a303bd76163793bd5968c72f5f4432

Original change's description:
> Redesign program key construction
>
> This does two things:
> 1) Moves responsibility for bit-packing portions of the key into the key
>    itself. A new GrKeyBuilder type manages adding bits, with asserts to
>    ensure a value always fits in the requested number. In theory this
>    will let us generate smaller keys overall, at the expense of slightly
>    more complex code during construction.
> 2) Adds a string label parameter for key methods that fold in data. For
>    new methods, the label is required. To ease migration, the old add32
>    does not require a label (yet). This will let us generate detailed,
>    human readable keys, either based on SK_DEBUG, or a runtime option
>    (if we're comfortable paying the cost).
>
> Bug: skia:11372
> Change-Id: Ib0f941551e0dbadabbd2a7de912b00e9e766b166
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/377876
> Commit-Queue: Brian Osman <brianosman@google.com>
> Reviewed-by: Brian Salomon <bsalomon@google.com>

Bug: skia:11372
Cq-Include-Trybots: luci.skia.skia.primary:Test-Win10-MSVC-Golo-GPU-QuadroP400-x86_64-Debug-All-Vulkan
Change-Id: I179ed581bc9ba772191e727274ac0ac6979ebdf3
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/378778
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
diff --git a/tools/gpu/MemoryCache.cpp b/tools/gpu/MemoryCache.cpp
index 93ef2b1..65f08b7 100644
--- a/tools/gpu/MemoryCache.cpp
+++ b/tools/gpu/MemoryCache.cpp
@@ -52,13 +52,13 @@
     return result->second.fData;
 }
 
-void MemoryCache::store(const SkData& key, const SkData& data) {
+void MemoryCache::store(const SkData& key, const SkData& data, const SkString& description) {
     if (LOG_MEMORY_CACHE) {
         SkDebugf("Store Key: %s\n\tData: %s\n\n", data_to_str(key).c_str(),
                  data_to_str(data).c_str());
     }
     ++fCacheStoreCnt;
-    fMap[Key(key)] = Value(data);
+    fMap[Key(key)] = Value(data, description);
 }
 
 void MemoryCache::writeShadersToDisk(const char* path, GrBackendApi api) {