RFR: 8315558: Undocumented exceptions in java.text.StringCharacterIterator

[Justin Lu]

Please review this PR and [CSR](https://bugs.openjdk.org/browse/JDK-8315558) which is a conformance change to document some exceptions in the specification of java.text.StringCharacterIterator.

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Commit messages:
 - copyright year
 - init

Changes: https://git.openjdk.org/jdk/pull/15547/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15547&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8315558
  Stats: 26 lines in 1 file changed: 14 ins; 6 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/15547.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15547/head:pull/15547

PR: https://git.openjdk.org/jdk/pull/15547