Modify api_config.py to generate a test config file and create a basic configuration for use in the POC test

Currently WiredTiger has an api_data.py and an api_config.py the first defines the WiredTiger API configuration which then gets turned into C by the second.

For our stress testing framework we'd like to use the same API however we don't want to share the same api_data.py file.

The work here is to create a test_data.py file which is read in by api_config.py and executed via s_all. It will create a test_config.c in test/cppsuite and a test_config.h (if necessary) also in test/cppsuite.

To validate it is working as expected the existing POC cpp test should have a basic config created which changes the default db directory.