RFR: 8227529: With malformed --app-image the error messages are awful

Thu Nov 30 14:20:16 UTC 2023

Add tests to make sure jpackage emits meaningful error messages when used with invalid app images.

Added `JPackageCommand.nullableOutputBundle()` function that returns an empty `Optional` instance if it fails to deduce a path to the output bundle from jpackage command line. This is the case when jpackage command is used with `--app-image` cli option and referenced app image directory is missing `.jpackage.xml` file.

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Commit messages:
 - 8227529: With malformed --app-image the error messages are awful

Changes: https://git.openjdk.org/jdk/pull/16901/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16901&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8227529
  Stats: 71 lines in 3 files changed: 64 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/16901.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16901/head:pull/16901

PR: https://git.openjdk.org/jdk/pull/16901