Adds a separate board for native64 instead of the `NATIVE_64BIT` workaround.
The files in `boards/native64` are more or less dummy files and just include
the `boards/native` logic (similar to `openlabs-kw41z-mini-256kib`).
The main logic for native is in `makefiles/arch/native.inc.mk`, `cpu/native`
and `boards/native`.
The remaining changes concern the build system, and change native board checks
to native CPU checks to cover both boards.
* Added arch_64bit feature and added it to all packages that require 32 bit.
* hacl, wolfssl: Fixed different types between function declaration and implementation.
* lwip: Add required flag for 64 bit and bug fix in `lwip_sock`.
* micro-ecc: Workaround for GCC warning when using `__int128`.
