Migrate build process to PEP 621/517 compliance

[mg-twentyone]

Description

This PR updates the packaging and build system of bdkpython to align with modern Python packaging standards via pyproject.toml.
Changes:

• Update pyproject.toml file according to PEP 621 and PEP 517
• Removed the legacy setup.py file and usage
• Add metadata such as keywords, classifiers, and URLs
• Ensure the correct inclusion of Rust extension via [tool.setuptools-rust]
• Update README.md file by including the new build process.

Fixes #12

Changelog notice

This pull request breaks the current building wheel process

Bugfixes:

• This pull request breaks the existing API
• I've added tests to reproduce the issue which are now passing
• I'm linking the issue being fixed by this PR

[thunderbiscuit]

Hey this is awesome stuff @mg-twentyone! Are you on our Discord server for BDK? If so please send me a DM!

[mg-twentyone]

hey @thunderbiscuit. I noticed a bug with the new configuration (project.toml) using setuptools-rust to include the Rust library. I am working to fix it. I will also try to update the workflow in the GitHub Actions by updating the build process for different operating systems. I joined the Discord channel, feel free to reach to me whenever you want. I will get in touch with you as soon as I finish it to provide u with all the details and simplify the review process.

[thunderbiscuit]

I have tested this and it works flawlessly. I'm impressed! Big update. I'd love to leave time for @reez to take a look, and maybe one of our production users to also take a look if he has time (@andreasgriffin).

Overall I think this is a major improvement! A few questions are left for me, particularly regarding the naming of the wheels (this is not new and not related to this PR so I don't think of it as a blocker though). But it just feels like the whole "you have to name your artifact with the correct string otherwise pip will not consider it valid for a given platform" (instead of leveraging package metadata) is super weird and cannot possibly be optimal. Anywa this is probably for a follow-up issue or PR because it's a long-standing issue with how we build and release this library. It works, but... yeah.

While we wait for review, 2 little things you can do @mg-twentyone:

1. This PR needs a rebase on master
2. The commits' messages will have to be slightly fixed to follow the BDK convention (conventional commits, with all lowercase lettering if possible).