RFR: 8362598: [macos] Add tests for custom info plist files

[Alexey Semenyuk]

On Fri, 26 Sep 2025 02:54:32 GMT, Alexander Matveev <almatvee at openjdk.org> wrote:

> - Added test for custom info plist to cover app image including embedded runtime and runtime installer.
> - Fixed bug in `writePList`. It was missing `writeStartDocument()/writeEndDocument()` and `DOCTYPE` should be full xml string.

In the case of an app bundle, there is a single test case that replaces both the main and the runtime plist files. We need three test cases for better coverage:
 - custom main plist file
 - custom runtime plist file
 - custom main and runtime plist files

The tests don't cover pattern matching in custom plist files. E.g., jpackage will replace `DEPLOY_LAUNCHER_NAME` pattern in the main plist file with the main launcher name; jpackage will replace `CF_BUNDLE_VERSION` pattern in the runtime plist file with the app version. We need to test that jpackage replaces these patterns in custom plist files in the same way it does for the default plist files.

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PR Comment: https://git.openjdk.org/jdk/pull/27509#issuecomment-3338327519