[Python] Allow configuration options to be set when creating BallistaContext

**Is your feature request related to a problem or challenge? Please describe what you are trying to do.**
The Python bindings for BallistaContext have hard-coded configuration settings that cannot be overridden, so it is not possible to tune jobs.

**Describe the solution you'd like**
Allow configuration options to be set when creating BallistaContext

**Describe alternatives you've considered**
None

**Additional context**
None

Begin by locating the Python binding entry point for BallistaContext and the hard-coded configuration settings it uses. Define the supported creation-time option input and verify that a supplied value overrides the default and reaches job execution.

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