[PATCH v8] eal: RTE_PTR_ADD/SUB char* for compiler optimizations

[Scott Mitchell]

> Looks good to me and not too complex.
>
> AI code review had some additional comments.

I fixed the import order, the build failure (due to recent changes in
REGISTER_FAST_TEST), and submitted v9. Please let me know if you feel
any of the other items are blocking and must be resolved. I held off
on release notes for now as I would also like to get
https://patches.dpdk.org/project/dpdk/patch/20260112120411.27314-3-scott.k.mitch1@gmail.com/
merged which makes unaligned typedefs safe for general use and direct
pointer arithmetic (less risk of PTR ADD/SUB macros confusing
compilers as Morten also found).