RFR: JDK-8317612: ChoiceFormat and MessageFormat constructors call non-final public method [v4]

[Justin Lu]

> Please review this PR which updates ChoiceFormat and MessageFormat to no longer call overridable methods in their constructors.
> 
> The overridable methods called in the constructors are: _ChoiceFormat::applyPattern_, _ChoiceFormat::setChoices_, and _MessageFormat::applyPattern_. The code should be updated so that both the methods and constructors call a separate private method. Some other drive-by cleanup changes were included in the change as well.

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

  re-apply 'final' to the static methods in ChoiceFormat

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Changes:
  - all: https://git.openjdk.org/jdk/pull/16064/files
  - new: https://git.openjdk.org/jdk/pull/16064/files/74847121..a44ea641

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16064&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16064&range=02-03

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/16064.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16064/head:pull/16064

PR: https://git.openjdk.org/jdk/pull/16064