RFR: 8265989: System property for the native character encoding name

[Roger Riggs]

On Wed, 28 Apr 2021 22:24:31 GMT, Naoto Sato <naoto at openjdk.org> wrote:

> After some internal discussion, we thought it was good to expose the native environment's default character encoding, which Charset.defaultCharset() is currently based on. This way applications will have a better migration path after the [JEP 400](https://openjdk.java.net/jeps/400) is implemented, in which Charset.defaultCharset() will return UTF-8, but the value of this new system property will remain intact. A [CSR](https://bugs.openjdk.java.net/browse/JDK-8266075) has been filed with more detailed information.

To support the statement that changing the property has no effect.
Please add it to the jdk.internal.util.StaticProperties cached values and an internal access method.

Otherwise looks good.

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PR: https://git.openjdk.java.net/jdk/pull/3777