RFR: 8320692: Null icon returned for .exe without custom icon [v2]

[Alexander Zuev]

> Replaced asserts with NullPointerException calls because outside of testing that would be more informative - i do not think many people running their applications with assertions in system libraries enabled;
> Added a code that will analyze the result of the getIcon and will fall back to the default icon for the file type retrieved from the ShellFolder;
> Added a test case made by Aleksei Ivanov.

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

  Revert NPE to asserts
  Move null check inside the loop so we do not retrieve extra
  icons if we encounter a null one

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Changes:
  - all: https://git.openjdk.org/jdk/pull/17475/files
  - new: https://git.openjdk.org/jdk/pull/17475/files/1640fbb1..b9e453de

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17475&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17475&range=00-01

  Stats: 14 lines in 1 file changed: 3 ins; 7 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/17475.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17475/head:pull/17475

PR: https://git.openjdk.org/jdk/pull/17475