Switch to pyproject.toml based build

[chandanchowdhury]

As mentioned in #1016 setup.py based builds are being deprecated in favor of pyproject.toml based builds.

Important notes:

• The build detects the package version dynamically using Git commit and tags, so had to remove .git from .dockerignore for the Python package build to succeed during Docker build.
• However, the Docker build using Docker.multistage is multi-stage. The builder stage builds the Python package from source code. The next runner stage installs the package built in builder stage.
• Changed .github/workflows/test_suite.yml to use the new Dockerfile.multistage. Need to update publish-to-ghcr.yml when we are satisfied with the multi-stage Docker build.
• Added Pipfile and Pipfile.lock in case someone wants to start using pipenv or we ourselves do so in future to keep our development environment clean.

[chandanchowdhury]

Review request

@achantavy