RFR: 8320655: awt screencast robot spin and sync issues with native libpipewire api

[Anton Bobrov]

This patch addresses the issues described in the https://bugs.openjdk.org/browse/JDK-8320655 by fixing the proper locking and signalling around libpipewire thread loop condition variables and also fixing libpipewire error detection and signalling and propagation to the screencast API. This makes the screencast robot stable enough to consistently make it thru the entire javax/swing jtreg suite without hanging and also significantly reduces CPU consumption as there is no longer any burning spinners since they are now waiting on related conditions proper.

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Commit messages:
 - 8320655: awt screencast robot spin and sync issues with native libpipewire api

Changes: https://git.openjdk.org/jdk/pull/16794/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16794&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8320655
  Stats: 30 lines in 1 file changed: 27 ins; 2 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/16794.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16794/head:pull/16794

PR: https://git.openjdk.org/jdk/pull/16794