vpx_image: round chroma height for external odd-height buffers

vpx_img_wrap() leaves external image heights unrounded, but
vpx_img_set_rect() uses a floor-divided chroma height to locate the
second planar chroma plane. With an odd image height, the second
plane starts one row early and aliases the last row of the first.

Round the chroma height up when advancing between planar U and V
data, and cover the affected 8-bit and high-bit-depth formats with
a regression test.

Assisted-by: OpenAI Codex
Change-Id: I76fd32297c9e58e273b533606fd98bd683ba8072