RFR: 8282819: Deprecate Locale class constructors

[Naoto Sato]

Proposing to deprecate the constructors in the `java.util.Locale` class. There is already a factory method and a builder to return singletons, so there is no need to have constructors anymore unless one purposefully wants to create `ill-formed` Locale objects, which is discouraged. We cannot terminally deprecate those constructors for the compatibility to serialized objects created with older JDKs. Please see the draft CSR for more detail.

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Commit messages:
 - 8282819: Deprecate Locale class constructors

Changes: https://git.openjdk.java.net/jdk/pull/7947/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7947&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8282819
  Stats: 904 lines in 196 files changed: 74 ins; 22 del; 808 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7947.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7947/head:pull/7947

PR: https://git.openjdk.java.net/jdk/pull/7947