Config-level size
I added `config-size` job and using #909 I implemented the fan-in `dataset-size` job.

I remember there was a discussion to name it `dataset--size` at one point. Not the biggest fan but lmk

It also returns `size: {...}` and not `sizes: {...}` as before.
Config-level size: I added `config-size` job and using #909 I implemented the fan-in `dataset-size` job.

I remember there was a discussion to name it `dataset--size` at one point. Not the biggest fan but lmk

It also returns `size: {...}` and not `sizes: {...}` as before.