Switch from cx_oracle to oracledb

[ximenesuk]

This pull request replaces cx_Oracle libraries with oracledb and bumps the minimum Python version to 3.9

The brute force approach of globally replacing cx_Oracle with oracledb and adding cffi as a dependency resulted in all the tests passing. In addition the setup.py file has been updated to the new libraries. The requirements.txt file has also been updated. As an aside all has been added to setup uptions.

To test:

• [x] etlhelper should pip install from this branch (with all option as additional test)
  • pip install git+https://github.com/BritishGeologicalSurvey/etlhelper@oracledb#egg=etlhelper[all]
  • pip install git+https://github.com/BritishGeologicalSurvey/etlhelper@oracledb#egg=etlhelper[oracle]
• [x] all tests should pass
• [x] the documentation should reflect the new libraries

Closes #140 and #160

[sophie-taylor]

I've tested this request on various scripts and all passed fine. Ready to commit

[leorudczenko]

I've just been going through other files to change for #158, and it seems there are still some mentions of the old setup_oracle_client in CONTRIBUTING.md and potentially bin/run_tests_for_developer.sh too.

Also, should this merge request be for for_v1 rather than main?

[volcan01010]

OK, well spotted. I'll change the target branch and update the docs.

[volcan01010]

This all works for me and I'm happy to merge into for_v1.

Note that https://github.com/BritishGeologicalSurvey/etlhelper/issues/110 discusses handling LOBs in a different way. We should experiment with this now and decide what the default setting should be.