[Dev] Move PyArrow filter pushdown to separate file

[Tishj]

This has annoyed me for some time, needing to remember the filter pushdown logic is defined in arrow_array_stream.cpp which is completely illogical

Cleaned it up, added a Makefile for make format-main, and extended the import cache to get rid of some raw py::_module::import calls

[evertlammerts]

Ha, love it, frustration driven cleanup, go for it :-)

Re Makefile: I have a relatively strong preference to not have one here unless we must, and then not one that depends on scripts in the duckdb submodule. I have a branch where I'm adding the linting and formatting rules. I'm planning to add pre-commit there to run all clang-format and clang-tidy stuff. That integrates nicely with git workflows and CI. I'm hoping to merge this post the 1.4.0 release.

[Tishj]

Sure, using a Makefile is kind of "the duckdb way", so not having one entirely is kind of creating friction for duckdb maintainers to come in and contribute here, which is something to be aware of

But I'll rip it out for now