Do not merge or delete: Py36 compatibility branch

[haakonvt]

Description

It was requested that a newer version of the SDK was made Py36 compatible. This branch is it.

Note

1. There are quite a few breaking changes going from v2 to v5. The most important are:
   1. v4 brought new credential classes: https://cognite-sdk-python.readthedocs-hosted.com/en/latest/cognite.html#authenticate
   2. v5 overhauled datapoints fetching: https://github.com/cognitedata/cognite-sdk-python/blob/master/MIGRATION_GUIDE.md
2. Be careful trusting to_pandas conversions. Do not use retrieve_dataframe with uniform_index=True unless you use pandas >= 1.4 (requires PY38 😉 )
3. Missing API: Context

How to pip install:

pip install git+https://github.com/cognitedata/cognite-sdk-python@py36-compat

Other

Ref. internal slack: https://cognitedata.slack.com/archives/C0252J883DG/p1677671617290589