[ci] [python-package] move tool configuration to pyproject.toml

[jameslamb]

Contributes to #3867.
Contributes to #4308.
Contributes to #5061.

Proposes moving configuration for all Python linting tools that support it into pyproject.toml (and for flake8, which doesn't support it per PyCQA/flake8#234, into setup.cfg).

Also adds configuration to skip running linters over the lightgbm-python/ directory (new local build directory introduced in #5837), to help with local development.

Notes for Reviewers

Many Python tools have been moving in this direction, ever since PEP 518 was accepted back in 2016.

From the PEP (link) ...

The [tool] table is where any tool related to your Python project, not just build tools, can have users specify configuration data as long as they use a sub-table within [tool], e.g. the flit tool would store its configuration in [tool.flit].

And projects using those tools have followed. For example, dmlc/xgboost#9112.

Benefits of this Change

Sets up pyproject.toml and setup.cfg as sources of configuration for the Python project, reducing the size of the diff to be reviewed in #5759.

Puts tool configuration into a format used by many other Python projects, making it a bit easier (I hope) for new contributors to work on LightGBM.

[jameslamb]

closing and re-opening to try to get rid of that license/cla check 🙃

[github-actions]

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