Mb/charge exchange kernel new

[mbukaea]

Description

Please include a summary of changes, motivation and context for this PR.

Fixes #178 Fixes #194

Type of change

Please delete options that are not relevant.

• [ ] New feature (non-breaking change which adds functionality)
• [ ] Requires documentation updates

Testing

Please describe the tests that you ran to verify your changes and provide instructions for reproducibility. Please also list any relevant details for your test configuration.

• [ ] Test Foo in /test/path/to/file_for_test_Foo.cpp
  • Description of test Foo
• [ ] Test Bar in /test/path/to/file_for_test_Bar.cpp
  • Description of test Bar

Test Configuration:

• OS:
• SYCL implementation:
• MPI details:
• Hardware:

Checklist:

• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] New and existing unit tests pass locally with my changes
• [ ] Any new dependencies are automatically built for users via cmake
• [ ] I have used understandable variable names
• [ ] I have run clang-format against my *.hpp and *.cpp changes
• [ ] I have run cmake-format against my changes to CMakeLists.txt
• [ ] I have run black against changes to *.py
• [ ] I have made corresponding changes to the documentation
• [ ] I have performed a self-review of my own code
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] My changes generate no new warnings