Replace cx_Oracle with python-oracledb

Description

The title says it all: this MR replaces the cx_Oracle dependency with python-oracledb.

See the commit message and issue #51 (closed) for more details.

In addition to being the new and updated version of the cx_Oracle
library, python-oracledb has the benefit to provide the so-called "Thin"
mode. Enabled by default, it avoids any dependency on the Oracle Client
libraries in most of the (basic) cases.

Related Issue

Fixes #51 (closed)

How Has This Been Tested?

Code runs seamlessly without requiring the Oracle Client libraries. The VFAT calibration constants output file is identical before and after this MR.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.