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ARROW-8440: [C++] Refine SIMD header files

- Include all necessary SIMD header files in a single header "simd.h".
- Simplify architecture dependent CRC code in hash_util.h.
- Remove SSEUtil namespace which contains some SSE constants.
  These codes are not used and I can't find proper place to hold them.
- Remove sse_util.h, neon_util.h, and hash_util.h.

Closes #6954 from cyb70289/simd

Authored-by: Yibo Cai <yibo.cai@arm.com>
Signed-off-by: Antoine Pitrou <antoine@python.org>