<Swing Dev> [jdk17] RFR: 8269269: [macos11] SystemIconTest fails with ClassCastException [v3]

[Alexander Zuev]

> Added check for the icon class type
> Added check if file or folder we are testing against exists and
> accessible
> Removed test from problem list

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

  Make test headless again
  Do not test assumption that icon on Windows is always a MultiResolution
  the specification does not state it and under some circumstances it is
  not.

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Changes:
  - all: https://git.openjdk.java.net/jdk17/pull/178/files
  - new: https://git.openjdk.java.net/jdk17/pull/178/files/28f2d43a..6537dca9

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk17&pr=178&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk17&pr=178&range=01-02

  Stats: 13 lines in 1 file changed: 1 ins; 10 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk17/pull/178.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk17 pull/178/head:pull/178

PR: https://git.openjdk.java.net/jdk17/pull/178