v3.0.0

Major refactoring with breaking changes.

Added

• Add support for ccache 3.7 and above, that comes with a new format for machine-readable statistics
• Add utilities to generate reference testdata using ccache on long-term-support Debian and Ubuntu releases

Changed

• Switch to main as the default Git branch
• Refactor ccache wrapper and shell abstractions to handle both formats:
  • pre-3.7 mixed configuration/statistics output (--show-stats)
  • 3.7 and above statistics (--print-stats) output
• Split Configuration and Statistics data
• Add a dedicated configuration parser
• Relocate Prometheus collector
• Bump Go to 1.19 for CI, Promu and Docker builds
• Switch to Github Actions
• Rewrite README and CHANGELOG in Markdown
• Refactor tests and test helpers to make it easier to add golden test cases
• Update Prometheus Makefile library