Restructure Pdf2Parquet with its own dpk_ namespace

[touma-I]

Why are these changes needed?

This is a first of a series of restructuring changes that are done to have each transform built as its own module (e.g. dpk_pdf2parquet) with a ray submodule (dpk_pdf2parquet.ray ).

Removed python and ray folders and keep Dockerfile.python and Dockerfile.ray
remove pyproject.toml and Makefiles
move python code under dpk_pdf2parquet
move ray code under dpk_pdf2parquet/ray
change import statement to include module name
replace recursive Makefile and use targets from .make.cicd.targets
adapt kfp_ray/Makefile and other make target

Related issue number (if any).

#774

[roytman]

@touma-I thank you for your work.

[shahrokhDaijavad]

@touma-I Please check what I have done before I make changes to the others. You seem to have only the run-cli-sample as a target for make, so I got rid of everything else that had to do with make other targets.
Do we need to provide an example of how to run the ray code?