RFR: 8298416: Console should be declared `sealed` [v4]

[Naoto Sato]

> `Console` class now has a couple of internal subclasses within `java.io` package. It should be `sealed` and subclasses be declared in the `permits` clause. The implementation resided in `Console` class is separated into `ConsoleImpl` class.

Naoto Sato has updated the pull request incrementally with one additional commit since the last revision:

  newUnsupportedOperationException(), cosmetic changes to method descs

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Changes:
  - all: https://git.openjdk.org/jdk/pull/11615/files
  - new: https://git.openjdk.org/jdk/pull/11615/files/93945d6f..f2b2335b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11615&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11615&range=02-03

  Stats: 208 lines in 1 file changed: 4 ins; 9 del; 195 mod
  Patch: https://git.openjdk.org/jdk/pull/11615.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11615/head:pull/11615

PR: https://git.openjdk.org/jdk/pull/11615