Consolidate GPU buffer implementations

Consolidates all the different buffer implementations into a single
GrBuffer class. This will allow us to add new buffer types, use DSA in
OpenGL, track buffer bindings by unique ID, cache buffers without
respect to the type of data they have been used for previously, etc.
This change is strictly a refactor; it introduces no change in
functionality.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1825393002

Committed: https://skia.googlesource.com/skia/+/8b1bff29675afd25843439eade634a57f68fe16f

Review URL: https://codereview.chromium.org/1825393002
diff --git a/src/gpu/gl/GrGLCaps.cpp b/src/gpu/gl/GrGLCaps.cpp
index 599a0e0..18e68e9 100644
--- a/src/gpu/gl/GrGLCaps.cpp
+++ b/src/gpu/gl/GrGLCaps.cpp
@@ -399,14 +399,14 @@
 
     // On many GPUs, map memory is very expensive, so we effectively disable it here by setting the
     // threshold to the maximum unless the client gives us a hint that map memory is cheap.
-    if (fGeometryBufferMapThreshold < 0) {
+    if (fBufferMapThreshold < 0) {
         // We think mapping on Chromium will be cheaper once we know ahead of time how much space
         // we will use for all GrBatchs. Right now we might wind up mapping a large buffer and using
         // a small subset.
 #if 0
-        fGeometryBufferMapThreshold = kChromium_GrGLDriver == ctxInfo.driver() ? 0 : SK_MaxS32;
+        fBufferMapThreshold = kChromium_GrGLDriver == ctxInfo.driver() ? 0 : SK_MaxS32;
 #else
-        fGeometryBufferMapThreshold = SK_MaxS32;
+        fBufferMapThreshold = SK_MaxS32;
 #endif
     }