meta: Implement ext_framebuffer_multisample_blit_scaled extension

Extension enables doing a multisample buffer resolve and buffer
scaling using a single glBlitFrameBuffer() call. Currently, we
have this extension implemented in BLORP which is only used by
SNB and IVB. This patch implements the extension in meta path
which makes it available to Broadwell.

Implementation features:
 - Supports scaled resolves of 1X, 2X, 4X and 8X multisample buffers.

 - Avoids unnecessary shader compilations by storing the pre compiled
   shaders for each supported sample count.

 - Uses bilinear filtering for both GL_SCALED_RESOLVE_FASTEST_EXT and
   GL_SCALED_RESOLVE_NICEST_EXT filter options. Although, extension
   allows this behavior, it'll be nice to use trilinear or anistropic
   filtering for GL_SCALED_RESOLVE_NICEST_EXT filter. I'll work on it
   after pushing this series.

Signed-off-by: Anuj Phogat <anuj.phogat@gmail.com>
i965: Enable EXT_framebuffer_multisample_blit_scaled for gen8

Signed-off-by: Anuj Phogat <anuj.phogat@gmail.com>