[jdk17u-dev] RFR: 8288589: Files.readString ignores encoding errors for UTF-16

[Goetz Lindenmaier]

I backport this for parity with 17.0.8-oracle.

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Commit messages:
 - Backport 2728770e3d73bb11c4d6e54b5aff91588a1a780b

Changes: https://git.openjdk.org/jdk17u-dev/pull/1230/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=1230&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8288589
  Stats: 231 lines in 4 files changed: 143 ins; 68 del; 20 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/1230.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/1230/head:pull/1230

PR: https://git.openjdk.org/jdk17u-dev/pull/1230