mediapy `display_images()` downsamples images seemingly arbitrarily....

Issue tested with version: https://github.com/google/mediapy/pull/41

a) If I call `media.show_images()` once passing it a dict of 32 images, each with shape (512, 512, 3), it stubbornly displays a row matrix of images that are (256, 256, 3) each.

b) If I call `media.show_images()` 32 times passing it a dict with a single image each time, each with shape (512, 512, 3), it displays the images at the correct resolution (however the images are displayed one below each other which is not what I want).

c) In case a), if I pass the argument `height=512` then the images are displayed pixelated 2x: it looks like mediapy makes a 256x256 internal image buffer and displays it pixelated at 512x512.

d) Passing `downsample=False` doesn't fix the issue either (too easy-no points).

e) I also have a repro case where it dowsamples from 480 to 240 so this seems like a 2x downsample bug.

f) Aha!!! It looks like displaying a smaller number of images (6 vs. 32) works as intended.

Looks like it is some kind of cap on total memory it can consume?