[Feature Request] Add ECB mode for AES

[LaRiffle]

AES in CTR mode is great, but for some applications ECB mode would be very useful.
I know part of this work is inspired from https://github.com/kokke/tiny-AES-c which implements CTR, ECB and CBC, so I don't know how hard it would be to have support for ECB.

I'm not sure how the exact torch api would look like, I don't even know if it's ok to add a new functionto torch, it could also probably be a csprng function instead, with a name inspired from kokke/tiny-AES-c syntax.