<i18n dev> RFR: 8320919: Clarify Locale related system properties [v2]

[Naoto Sato]

> This is a doc change to clarify what the `Default Locale` is, and how it is established during the system startup using the system properties. Those locale-related system properties have existed since the early days of Java, but have never been publicly documented before. It is also the intention of this PR to clarify those system properties and how they are overridden. A corresponding CSR has been drafted.

Naoto Sato has updated the pull request incrementally with four additional commits since the last revision:

 - Update src/java.base/share/classes/java/util/Locale.java
   
   Co-authored-by: Justin Lu <Justin.lu at oracle.com>
 - Update src/java.base/share/classes/java/util/Locale.java
   
   Co-authored-by: Justin Lu <Justin.lu at oracle.com>
 - Update src/java.base/share/classes/java/util/Locale.java
   
   Co-authored-by: Justin Lu <Justin.lu at oracle.com>
 - Update src/java.base/share/classes/java/util/Locale.java
   
   Co-authored-by: Justin Lu <Justin.lu at oracle.com>

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/17065/files
  - new: https://git.openjdk.org/jdk/pull/17065/files/b2614b17..4f5980bc

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17065&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17065&range=00-01

  Stats: 4 lines in 1 file changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/17065.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17065/head:pull/17065

PR: https://git.openjdk.org/jdk/pull/17065