GS: only flush queued draws for an upload the queue can see

GSTexture::Update drained the whole deferred-draw queue before every upload.
Almost none of those uploads touch a texture the queue has heard of - the
texture cache uploads into surfaces it just fetched from the pool - so the
flush was throwing away coalescing for nothing.

Use the narrow form, which flushes only when a queued draw actually reads or
writes this texture. That is the same test the pool and deferred-clear paths
already use.

Attributing every flush in a four-frame Dirge of Cerberus capture put uploads
at 46 of 305, second only to draws that carry a barrier. Removing them takes
the capture from 543 render passes to 523; the rest of the corpus is unmoved
and every frame hash is still identical to the unscheduled path.

pcsx2/GS/Renderers/Common/GSTexture.cpp

@@ -18,7 +18,11 @@ GSTexture::~GSTexture() = default;
 
 bool GSTexture::Update(const GSVector4i& r, const void* data, int pitch, int layer)
 {
-	g_gs_device->FlushDeferredDraws();
+	// An upload only conflicts with a queued draw that reads or writes this very texture -
+	// and the overwhelming majority are into a source the queue has never seen, since the
+	// texture cache uploads into freshly pooled surfaces. Flushing for all of them was 15%
+	// of every flush on Dirge of Cerberus.
+	g_gs_device->FlushDeferredDrawsFor(this);
 	return DoUpdate(r, data, pitch, layer);
 }