RFR: 8370100: Redundant .png files in Linux app-image cause unnecessary bloat

[Alexey Semenyuk]

Don't put the default icon (.png) files in the app image on Linux.

Moving the nested Additional `Launcher.PropertyFile` class at the top level caused most changes in the test code.

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Commit messages:
 - DefaultLauncherIcon: blessed-modifier-order.sh  fix
 - FileAssociations: revert redundant change
 - Fix fa icon verification on Linux
 - PropertyFile: import clean up
 - Move PropertyFile to the package level and make it not throw IOException.
 - LinuxPackagingPipeline, WinPackagingPipeline: remove unused normalizeShortcuts() methods
 - IconTest: revamp
 - LinuxHelper: revamp
 - Don't add the default launcher icon to app image on Linux
 - Make Launcher interface provide complete information about the source of the launcher icon; Before this change, the function getting a resource for an additional launcher icon took both the additional launcher and the main launcher as input. Now its result doesn't depend on the main launcher.

Changes: https://git.openjdk.org/jdk/pull/27928/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27928&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8370100
  Stats: 675 lines in 30 files changed: 493 ins; 89 del; 93 mod
  Patch: https://git.openjdk.org/jdk/pull/27928.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27928/head:pull/27928

PR: https://git.openjdk.org/jdk/pull/27928