RFR: 8362598: [macos] Add tests for custom info plist files [v5]

[Alexander Matveev]

> - 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.

Alexander Matveev has updated the pull request incrementally with one additional commit since the last revision:

  8362598: [macos] Add tests for custom info plist files [v5]

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/27509/files
  - new: https://git.openjdk.org/jdk/pull/27509/files/267bd365..01e41f1f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27509&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27509&range=03-04

  Stats: 23 lines in 1 file changed: 21 ins; 2 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/27509.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27509/head:pull/27509

PR: https://git.openjdk.org/jdk/pull/27509