feat: add dockerfile output for Python builds

[AbhinavPradeep]

Summary

Adds option "dockerfile" to the --output-format flag for gen-build-spec. For Python packages, it generates a dockerfile built on the oraclelinux:9 image to rebuild the package.

Description of changes

• Modified build_spec_generator.py to add functionality to infer the latest Python interpreter version satisfying the packages constraints, and generate a dockerfile that would build that Python interpreter from source. The dockerfile then proceeds to use that built interpreter to build the package itself.

[behnazh-w]

• Please add an example for this new feature to the docs/source/pages/tutorials/rebuild_third_party_artifacts.rst tutorial.
• Add the docker format to the --output-formatCLI arg description.
• Update docs/source/pages/cli_usage/command_gen_build_spec.rst.

[behnazh-w]

Please add an integration test for the docker package used in the tutorial, and use the tutorial tag. For now, we can just compare the dockerfile output with the expected Dockerfile.