RFR: 8333775: Small improvement to outputStream auto-indentation mode

[Matthias Baesken]

On Fri, 7 Jun 2024 08:40:22 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

> Almost trivial enhancement.
> 
> [JDK-8333211](https://bugs.openjdk.org/browse/JDK-8333211) added automatic indentation. Some changes to complement that:
> 
> - let outputStream::set_autoindent() return the old value for later restoration
> - add an RAII object to enable autoindent and restore the old state when leaving.

Marked as reviewed by mbaesken (Reviewer).

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

PR Review: https://git.openjdk.org/jdk/pull/19592#pullrequestreview-2107320315