RFR: 8287541: Files.writeString fails to throw IOException for charset "windows-1252"

[Naoto Sato]

The code path calls `String.getBytesNoRepl()`, but it blindly replaces unmappable characters with replacements if the encoder is an `ArrayEncoder`. Changed only to do so if `doReplace` is `true` in `String.encodeWithEncoder()`.

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Commit messages:
 - 8287541: Files.writeString fails to throw IOException for charset "windows-1252"

Changes: https://git.openjdk.java.net/jdk/pull/9019/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=9019&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8287541
  Stats: 22 lines in 2 files changed: 4 ins; 11 del; 7 mod
  Patch: https://git.openjdk.java.net/jdk/pull/9019.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/9019/head:pull/9019

PR: https://git.openjdk.java.net/jdk/pull/9019