RFR: 8353585: Provide ChoiceFormat#parse(String, ParsePosition) tests [v2]

[Justin Lu]

> Please review this PR which provides unit tests for `ChoiceFormat#parse(String, ParsePosition)` to check default, multi match, and no match behavior. There were no existing relevant tests.

Justin Lu has updated the pull request incrementally with one additional commit since the last revision:

  Naoto's review - neg and exceeding length PP index cases

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Changes:
  - all: https://git.openjdk.org/jdk/pull/24395/files
  - new: https://git.openjdk.org/jdk/pull/24395/files/b9d6349c..1fb6a7a8

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=24395&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=24395&range=00-01

  Stats: 2 lines in 1 file changed: 2 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/24395.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24395/head:pull/24395

PR: https://git.openjdk.org/jdk/pull/24395