Copy Self to observability shared package

[potiuk]

Shared packages should not refer to airflow or airflow.sdk. This is the last "airflow" import remaining in the observability package.

Fixed during implementation of #58825

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[potiuk]

cc: @xBis7

[xBis7]

Nice and simple fix. It makes sense to duplicate the code since I can see that only observability uses it from shared. LGTM!

[amoghrajesh]

Since its only used for type checking, cant we just add the "typing-extensions" path?

[potiuk]

Since its only used for type checking, cant we just add the "typing-extensions" path?

I think not - I prefer not to depend on "typing-extensions" version of "Self" when we are already on Python 3.11+ in this case. Also having it this way makes it easy to have "rolling deprecation removal". When we move to Python 3.11+ next October - we will know we have to remove this completely. If we import from typing_extensions - there is no obvious signal that we should remove this one.

[amoghrajesh]

Since its only used for type checking, cant we just add the "typing-extensions" path?

I think not - I prefer not to depend on "typing-extensions" version of "Self" when we are already on Python 3.11+ in this case. Also having it this way makes it easy to have "rolling deprecation removal". When we move to Python 3.11+ next October - we will know we have to remove this completely. If we import from typing_extensions - there is no obvious signal that we should remove this one.

Sounds ok, thanks.