RFR: 8260265: UTF-8 by Default [v8]

[Naoto Sato]

> This is an implementation for the `JEP 400: UTF-8 by Default`. The gist of the changes is `Charset.defaultCharset()` returning `UTF-8` and `file.encoding` system property being added in the spec, but another notable modification is in `java.io.PrintStream` where it continues to use the `Console` encoding as the default charset instead of `UTF-8`. Other changes are mostly clarification of the term "default charset" and their links. Corresponding CSR has also been drafted.
> 
> JEP 400: https://bugs.openjdk.java.net/browse/JDK-8187041
> CSR: https://bugs.openjdk.java.net/browse/JDK-8260266

Naoto Sato has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 15 additional commits since the last revision:

 - Removed "default" alias
 - Merge branch 'master' into JDK-8260265
 - Merge branch 'master' into JDK-8260265
 - Merge branch 'master' into JDK-8260265
 - Merge branch 'master' into JDK-8260265
 - Merge branch 'master' into JDK-8260265
 - Merge branch 'master' into JDK-8260265
 - Refined `file.encoding` description
 - Merge branch 'master' into JDK-8260265
 - Reflects comments
 - ... and 5 more: https://git.openjdk.java.net/jdk/compare/66c3531f...67e1d4a9

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4733/files
  - new: https://git.openjdk.java.net/jdk/pull/4733/files/7d5137d3..67e1d4a9

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4733&range=07
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4733&range=06-07

  Stats: 15450 lines in 595 files changed: 11498 ins; 2067 del; 1885 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4733.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4733/head:pull/4733

PR: https://git.openjdk.java.net/jdk/pull/4733