[CDF-25715] ⏭Replace requests with httpx (#1993)

# Description

Replacing `requests` with `httpx` in the Toolkit `HTTPClient`. 

* This will be done in the `cognite-sdk` `v8`.
* Httpx is faster 
* Has async support


## Changelog

- [x] Patch
- [ ] Skip

## cdf

### Improved

- Adding `httpx` as a dependency. This will do the requests in
purge/download/upload/migrate commands.

## templates

No changes.
