<i18n dev> RFR: JDK-8329118: Run MessageFormat additional subformat pattern tests under en_US locale [v4]

[Justin Lu]

> Please review this PR which updates two MessageFormat sub format related tests to be guaranteed to run under the `en_US` locale.
> 
> There exists locale that do not provide distinct instances for separate styles. For example, the `en_IN` locale provides the same LONG and SHORT compact number instances. The test data is built to test sub formats under the assumption that different styles do provide distinct instances.
> 
> As this is the case, these tests should be ran under a locale that does provide distinct instances for separate styles.

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

  drop loc field for US constant

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Changes:
  - all: https://git.openjdk.org/jdk/pull/18498/files
  - new: https://git.openjdk.org/jdk/pull/18498/files/bf99aa92..5e797fe4

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18498&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18498&range=02-03

  Stats: 21 lines in 2 files changed: 4 ins; 8 del; 9 mod
  Patch: https://git.openjdk.org/jdk/pull/18498.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18498/head:pull/18498

PR: https://git.openjdk.org/jdk/pull/18498