Setting up MacOS CI + CI overhaul

[Hardcode3]

📌 Setting up MacOS CI + CI overhaul

📄 Description

• Refactored CI into reusable composite actions for Linux, macOS, and Windows setup/build flows.
• Added shared GitHub summary helpers and dedicated LLVM coverage actions for HTML generation and publishing.
• Reworked PR workflow gating so expensive pre-merge jobs run only when:
  • the run-pre-merge-checks label is added
  • a new push (synchronize) happens while that label is already present
• Preserved minimal checks when the pre-merge label is absent, including after the label is removed and more commits are pushed.
• Added a dedicated main branch workflow to publish LLVM coverage.
• Simplified LLVM coverage tool detection in CMake so llvm-cov and llvm-profdata are resolved from the active Clang toolchain instead of being hardcoded in GitHub Actions.
• Made coverage generation rely on the CMake target dependency chain instead of rerunning tests manually during publish/report steps.
• Extended CMake presets with Windows ARM64 release support and updated related test presets.
• Updated CMake documentation to reflect the new presets and coverage workflow.

🧩 Type of Change

• 🔧 Build or CI/CD configuration