Enable Scikit-Build-Core Support

[ahnaf-tahmid-chowdhury]

Description

This PR introduces support for scikit-build-core, streamlining the build process and improving compatibility.

This is a minimal version of the PR, excluding manylinux support, to facilitate a faster review. The full PR can be found here.

Key Changes

Enable scikit-build-core support

• Updated pyproject.toml to use scikit-build-core instead of legacy methods.

CMake and Build Updates

• Updated CMakeLists.txt to support skbuild, ensuring compatibility with both scikit-build-core and native CMake builds.
• Added GenerateScript.cmake to handle executable files (openmc) on both Linux and macOS.
• Updated OpenMCConfig.cmake.in to integrate scikit-build-core.

Git and Packaging Improvements

• Removed ignoring of .h5 files from .gitignore as they are needed.
• Removed MANIFEST.in as it is no longer required.

CI and Docs Updates

• Updated Dockerfile: Removed the need to run CMake before pip install as scikit-build-core now handles it.
• Updated CI configuration files to fix build and test issues.
• Added necessary APT packages for ReadTheDocs to compile dependencies properly.

Python API Enhancements

• Added functions to __init__.py to retrieve OpenMC installation configuration from the Python side.