Code quality improvements
Description of changes:
- fix template issues that have become compiler errors in Clang 20
- reduce number of Clang-Tidy 20 diagnostics
- follow-up to !403 (merged)
- adjust codegen jinja templates for pystencils 1.3.7
- fix missing header includes and compiler warnings about uninitialized
block_offsetstruct members
- fix missing header includes and compiler warnings about uninitialized
- expose SIMD vector sizes
- this will help client codes implement compatible memory-aligned field allocators