Use more helpful package tools

In the OPTIMADE Gateway I've started using more package tools to cover issues that may occur with regards to security, static typing and linting.

I've essentially implemented CI and pre-commit hooks for bandit, safety, pylint, and mypy, along with keeping black and removing flake8.

These tools try to ensure we don't implement exploitable holes in the server, as well as make sure the types we write for parameters match up with what is used. safety also checks known vulnerability issues for our dependencies.

Furthermore, as is seen in the FastAPI repository itself, we can combine a lot of repo config and setup files into pyproject.toml, and only use that one file; nice! :)

Essentially, this issue represents a "clean up" of the repository, to keep ourselves in check, try to get better development and PRs, as well as ensure we provide a good and safe package for end-users.

No repository files or tests are named. Start by reviewing the existing CI, pre-commit, and package configuration, then compare the requested consolidation with the FastAPI pyproject.toml example. Done means the listed security, typing, linting, and formatting tools are configured consistently in CI and pre-commit, with redundant configuration removed.