<i18n dev> RFR: 8312411: MessageFormat.formatToCharacterIterator() can be improved

[Justin Lu]

Please review this change which makes `MessageFormat.formatToCharacterIterator` fail fast(er). The return statement is also modified to call  toArray() as `toArray(new T[0])` over `toArray(new T[size])`.

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Commit messages:
 - Initial commit

Changes: https://git.openjdk.org/jdk/pull/15035/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15035&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8312411
  Stats: 7 lines in 1 file changed: 1 ins; 5 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/15035.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15035/head:pull/15035

PR: https://git.openjdk.org/jdk/pull/15035