RFR: 8269384: Determine native byte order for StringUTF16 via ByteOrder

[Yi Yang]

Prefer using ByteOrder to compute byte order for StringUTF16 to determining byte order by native method StringUTF16.isBigEndian.

-------------

Commit messages:
 - replace

Changes: https://git.openjdk.java.net/jdk/pull/4596/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4596&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8269384
  Stats: 17 lines in 2 files changed: 3 ins; 13 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4596.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4596/head:pull/4596

PR: https://git.openjdk.java.net/jdk/pull/4596