Improved GitHub Action to run clang-format as part of clang-tidy
* Simplify clang-tidy workflow
* Added modernize-use-using, modernize-redundant-void-arg, readability-static-accessed-through-instance
* Add nolint for libecl typedefs
Update clang-tidy.yml to use clang-tidy-15 to be able to support c++20
Do not use OpenMP, as omp.h is not found during parsing
Remove modernize-use-nullptr, as this does not work with <=> (spaceship operator)
https://reviews.llvm.org/D95714
