RFR: 8298971: Move Console implementation into jdk internal package [v3]

[Naoto Sato]

> Moving the built-in implementation of `Console` from `java.io` package into `jdk.internal.io` package. It now implements `JdkConsole` interface and is accessed through `ProxyingConsole`.

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

  Replaced assert with requireNonNull

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Changes:
  - all: https://git.openjdk.org/jdk/pull/11729/files
  - new: https://git.openjdk.org/jdk/pull/11729/files/777c0dc0..1f6b4f4f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11729&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11729&range=01-02

  Stats: 4 lines in 1 file changed: 3 ins; 1 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/11729.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11729/head:pull/11729

PR: https://git.openjdk.org/jdk/pull/11729