RFR: 8295803: Console should be usable in jshell and other environments [v3]

[Naoto Sato]

> This is to allow Console to be used even when it is not attached to the platform provided terminal, such as the case when the standard input is redirected. `System.console()` now returns a Console implementation based on `jdk.internal.le` terminal by default, or jshell implementation if available. A corresponding CSR has been drafted.

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

  Added more tests, loading with doPrivileged()

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Changes:
  - all: https://git.openjdk.org/jdk/pull/11421/files
  - new: https://git.openjdk.org/jdk/pull/11421/files/3d2b01f6..4c38b01b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11421&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11421&range=01-02

  Stats: 137 lines in 5 files changed: 121 ins; 2 del; 14 mod
  Patch: https://git.openjdk.org/jdk/pull/11421.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11421/head:pull/11421

PR: https://git.openjdk.org/jdk/pull/11421