[jdk20] RFR: 8298425: System.console().readLine() hangs in jshell

[Jan Lahoda]

After https://bugs.openjdk.org/browse/JDK-8295803, JShell snippets like:

jshell> System.console().readLine()


hang, as the JLine console is used, and it cannot correctly read from the console while in the remote agent (due to input/output redirection setup for the agent). Until [JDK-8296454](https://bugs.openjdk.org/browse/JDK-8296454) is resolved, the JLine console should be disabled inside the remote agent.

As the default console requires an attached terminal, and there is no attached terminal inside the agent, `System.console()` should then return `null` inside the JShell's agent, which was the behavior before JDK-8295803.

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Commit messages:
 - 8298425: System.console().readLine() hangs in jshell

Changes: https://git.openjdk.org/jdk20/pull/11/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk20&pr=11&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8298425
  Stats: 44 lines in 2 files changed: 44 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk20/pull/11.diff
  Fetch: git fetch https://git.openjdk.org/jdk20 pull/11/head:pull/11

PR: https://git.openjdk.org/jdk20/pull/11