Allow Fermi blit accelerate to add src/dst to the cache if they don't exist already. Use ScratchBuffers in the software blit path.

src/common/scratch_buffer.h

@@ -23,7 +23,10 @@ public:
           buffer{Common::make_unique_for_overwrite<T[]>(initial_capacity)} {}
 
     ~ScratchBuffer() = default;
+    ScratchBuffer(const ScratchBuffer&) = delete;
+    ScratchBuffer& operator=(const ScratchBuffer&) = delete;
     ScratchBuffer(ScratchBuffer&&) = default;
+    ScratchBuffer& operator=(ScratchBuffer&&) = default;
 
     /// This will only grow the buffer's capacity if size is greater than the current capacity.
     /// The previously held data will remain intact.
@@ -87,6 +90,12 @@ public:
         return buffer_capacity;
     }
 
+    void swap(ScratchBuffer& other) noexcept {
+        std::swap(last_requested_size, other.last_requested_size);
+        std::swap(buffer_capacity, other.buffer_capacity);
+        std::swap(buffer, other.buffer);
+    }
+
 private:
     size_t last_requested_size{};
     size_t buffer_capacity{};