Combine Deepslate Side and Top textures

I like the idea of the Deepslate being a block that looks differently on the top and bottom seeing as it's a layered type of rock, however it's side texture still looks very artificial.

Combining the top and side texture and using that for the sides would result in a more natural and smooth looking texture without losing the intended effect.

This also makes Cobbled Deepslate more unique and useful.