Add support for Oracle databases & dialect in PyDough

What is required:
* Adding new Database enums & connector support.
* Updating transform bindings to work for Oracle functions.
* Ensuring there are comprehensive SQL generation unit tests for the dialect that cover the functions.
* Test infrastructure which includes (TPCH, TPCH custom, defog, defog custom, CI)
* User documentation for how to use PyDough with Oracle.