Alert system for performance changes

This MR adds ministat_runner Python module and friends to enable performance alerts in Mesa CI.

To know more about the underlying tools, please check alerts/description.mako

Extra changes

• Refactor gitlab.yml and requirements.txt to share report sending settings between mesa-ci-status and alerts packages
• Extract Gitlab issue utility functions into a new common package
• Make reports generate new issues if a new title is given

Report example

• Link: https://gitlab.freedesktop.org/gallo/mesa/-/issues/16
• Note: the confidence level was set to 80% for demonstration purposes, the results are not as accurate as the production level, which is set to be 99.5%.