RFR: 8320692: Null icon returned for .exe without custom icon [v3]

[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:

  Fixed indentation
  Test now checks for returned icon not to be null

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/17475/files
  - new: https://git.openjdk.org/jdk/pull/17475/files/b9e453de..83998a2e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17475&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17475&range=01-02

  Stats: 6 lines in 2 files changed: 4 ins; 0 del; 2 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