RFR: 8320919: Clarify Locale related system properties [v8]

[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 with a new target base due to a merge or a rebase. The pull request now contains 15 commits:

 - Reflects review comments
 - Reflects review comments
 - Reflects review comments
 - Reflects review comments
 - Review comments
 - 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>
 - 6th draft
 - ... and 5 more: https://git.openjdk.org/jdk/compare/1fde8b86...4a76c89c

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Changes: https://git.openjdk.org/jdk/pull/17065/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17065&range=07
  Stats: 81 lines in 1 file changed: 71 ins; 0 del; 10 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