radv: fix multisample image copies

radv: fix multisample image copies

Previously before fb077b0728, the LOD parameter was being used in place of the
sample index, which would only copy the first sample to all samples in the
destination image. After that multisample image copies wouldn't copy anything
from my observations.

This fixes some copy_and_blit CTS tests.

v3.1: - set lod to 0 for nir_txf_ms (Samuel)
v2: - use GLSL_SAMPLER_DIM_MS instead of 2D (Samuel)
    - updated commit description (Samuel)

Fix this properly by copying each sample in a separate radv_CmdDraw and using a
pipeline with the correct rasterizationSamples for the destination image.

Cc: 18.0 18.1 <mesa-stable@lists.freedesktop.org>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>