Revisit the sdk folder hierarchy for task sdk's

### Body

Quoting from: https://github.com/apache/airflow/pull/50964/files#r2103305886

Few proposals here:

```
airflow-sdk-go
airflow-sdk-python
```

or

```
airflow-sdk/
go/
python/
```

cc @potiuk @jscheffl @uranusjr

### Committer

- [x] I acknowledge that I am a maintainer/committer of the Apache Airflow project.

Start by reading the referenced discussion in pull request 50964 and compare the two proposed SDK directory layouts. Review the current task SDK hierarchy, then clarify and document the agreed structure for the Go and Python SDKs; done means the maintainers have selected one layout.

Written by the indexing model from the issue text.