Refactor ci action to use a matrix of options

[steve-downey]

Right now the ci.yml specifies a collection of configs to run the matrix build over. It would be better style to set the variables and let CI construct the cartesian product:

    strategy:
      matrix:
        clang-version: [17]
        os: [ubuntu-24.04]
        toolchain: [clang-17-toolchain.cmake, clang-18-toolchain.cmake, gcc-13-toolchain.cmake]
        

https://docs.github.com/en/actions/using-jobs/using-a-matrix-for-your-jobs

[neatudarius]

Agree that we should improve this.

• Note that we still have a specific parameter added for clang-19: asan_options: "new_delete_type_mismatch=0" or cmake_config: RelWithDebInfo.
• Also, it seems that C++26 won't work with gcc-13 (check WIP PR Improve local and CI flows #26).

TLDR: I think we can do a better arrangement here, but I think we still need to have explicit exceptions for some toolchains, so maybe it's OK to have current format.