Refactor/iso15118 charger interface

[SebaLukas]

Describe your changes

Changed all cmds and vars in iso15118_charger interface to snake_case and all types in iso15118_charger types to PascalCase.

Issue ticket number and link

In the iso15118_charger interface there is a wild mix between snake_case, camelCase & PascalCase.

Checklist before requesting a review

• [x] I have performed a self-review of my code
• [ ] I have made corresponding changes to the documentation
• [x] I read the contribution documentation and made sure that my changes meet its requirements