RFR: 8370156: Fix jpackage IconTest [v3]

[Alexey Semenyuk]

> Rework IconTest.
> 
> Verified it produces the output as expected.
> 
> It still will not catch [JDK-8370155](https://bugs.openjdk.org/browse/JDK-8370155). However, this is deliberate to avoid significant changes in the test and implementation in a single commit.

Alexey Semenyuk has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains two commits:

 - Rollback JDK-8370100 specific patch
 - IconTest: revamp

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Changes: https://git.openjdk.org/jdk/pull/27883/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27883&range=02
  Stats: 230 lines in 1 file changed: 90 ins; 62 del; 78 mod
  Patch: https://git.openjdk.org/jdk/pull/27883.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27883/head:pull/27883

PR: https://git.openjdk.org/jdk/pull/27883