[CDF-26220, CDF-26218] 🤖 Upload assets hierarchy (#2180)

# Description

Handling uploading of asset hierarchy by iterating over the file
multiple times. Note that the alternative would be to do a sort in
memory, but the data plugin is optimized for not exploding in memory
thus chose the iteration method.

## Changelog

- [x] Patch
- [ ] Skip

## cdf

### Improved

- [alpha] The `cdf data upload` command can now upload an asset
hierarchy. It does this by first uploading root assets, then one level
deep, two level deep, and so on.

## templates

No changes.


