Current sampling methods have off by one issues on full frame:

• Bilinear sampling do not fully sample bottom and left image border, creating edges.
• Single elem buffers are not sampled at all when they should be at least on the borders to smooth edges.
• EWA filtering is partially implemented on ReadBufferOperation, it needs to be moved to MemoryBuffer on full frame.

Furthermore they use wrap_pixel when it's rarely needed.

In order to not affect tiled implementation, this commit creates
specific sampling methods for full frame needs.