Replace Pylint with Ruff for Python linting

[edespino]

• Remove Pylint installation, configuration, and invocation from the Makefile.

• Remove the GPL-licensed tarball: gpMgmt/bin/pythonSrc/ext/pylint-0.21.0.tar.gz

• Remove the old Pylint configuration file (.rcfile) since it is no longer relevant.

• Introduce Ruff installation via the official installation script.

• Dynamically install Ruff instead of storing tarballs or source files.

• Update checkcode target to run Ruff instead of Pylint.

• Clean up references to Pylint tarballs in the clean/distclean target.

• Update LICENSE and add license/LICENSE-ruff.txt

• Add new pyproject.toml file to configure Ruff:

  [tool.ruff] line-length = 88

  [tool.ruff.lint] select = ["E", "F", "W"]

Note: Ruff installation requires internet access during the first run.

Note: The removal of the Pylint .rcfile requires eventual replacement with corresponding Ruff configuration enhancements if more complex rules are needed in the future.

This change only introduces Ruff into the workflow. It does not attempt to fix or address any issues that Ruff may report.