RFR: JDK-8300783: Consolidate byteswap implementations [v5]

[Justin King]

> Deduplicate byte swapping implementations by consolidating them into `utilities/byteswap.hpp`, following `std::byteswap` introduced in C++23. Further simplification of `Bytes` will follow in https://github.com/openjdk/jdk/pull/12078.

Justin King has updated the pull request incrementally with one additional commit since the last revision:

  Add XL C/C++ builtins
  
  Signed-off-by: Justin King <jcking at google.com>

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Changes:
  - all: https://git.openjdk.org/jdk/pull/12114/files
  - new: https://git.openjdk.org/jdk/pull/12114/files/ef87529d..9986ce35

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12114&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12114&range=03-04

  Stats: 61 lines in 1 file changed: 58 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/12114.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12114/head:pull/12114

PR: https://git.openjdk.org/jdk/pull/12114