cmake: Added more x86_64 CPU backends when building with `GGML_CPU_ALL_VARIANTS=On` (#18186)
* minor: Consolidated `#include <immintrin.h>` under `ggml-cpu-impl.h`
* cmake: Added more x86-64 CPU backends when building with `GGML_CPU_ALL_VARIANTS=On`
- `ivybridge`
- `piledriver`
- `cannonlake`
- `cascadelake`
- `cooperlake`
- `zen4`
Resolves: #17966