<i18n dev> RFR: 8347949: Currency method to stream available Currencies [v7]

[Justin Lu]

> Please review this PR and CSR which adds a method to _java.util.Currency_ which returns a stream of the available Currencies.
> 
> The motivation can be found in the CSR.

Justin Lu has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains eight additional commits since the last revision:

 - make 'available' un-volatile
 - Merge branch 'master' into 8347949-Currency-Stream
 - reflect feedback
 - provide message for test assertion
 - reflect Roger's review
 - init hashset w/ accurate size via HashSet.newHashSet(int)
 - synchronize init method over block
 - init

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/23165/files
  - new: https://git.openjdk.org/jdk/pull/23165/files/96e86c80..ade21c92

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=23165&range=06
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23165&range=05-06

  Stats: 21807 lines in 2152 files changed: 10604 ins; 5415 del; 5788 mod
  Patch: https://git.openjdk.org/jdk/pull/23165.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23165/head:pull/23165

PR: https://git.openjdk.org/jdk/pull/23165