[CDF-25973] 🙂 Create SourceSystem (#2108)

# Description

**Context**: This is part of the `alpha` migration tooling in Toolkit,
for overview [see
here](https://cognitedata.atlassian.net/wiki/spaces/~170890702/pages/5455773697/Migration+Tooling+in+Toolkit).
This is a new step between 2 and 3.

Before we can migrate assets/event/files/timeseries/sequences, we need
to have a destination target space as well as CogniteSourceSystems
created.

<img width="989" height="312" alt="image"
src="https://github.com/user-attachments/assets/0016082e-4b49-413b-b4a8-ed611d4a0c66"
/>


## Changelog

- [x] Patch
- [ ] Skip

## cdf

### Added

- [alpha] This adds `cdf migrate sourec-system` which create
CogniteSourceSystem from the `source` properties of assets, events, and
files.

## templates

No changes.


