RFR: 8343128: PassFailJFrame.java test result: Error. Bad action for script: build}

[Alexey Ivanov]

After updating documentation for `PassFailJFrame.java` in [JDK-8340785](https://bugs.openjdk.org/browse/JDK-8340785) / #21162, jtreg interprets the file as a test because it finds `@test` tag in the file. This results in a failed test.

I didn't find a way to avoid this problem when using [`@snippet` feature](https://docs.oracle.com/en/java/javase/21/javadoc/programmers-guide-snippets.html#GUID-1B435AA6-84D5-4693-AF5E-6470EEE970FC) of the javadoc (see also [JavaDoc Code Snippet API - Sip of Java](https://inside.java/2022/04/04/sip46/), so I used the old friends `<pre><code>`.

Now, `@` is represented as an HTML character entity, and jtreg no longer finds the `@test` marker in the file.

With this update, I inlined the end comment into the same code block with `/` represented as a character entity. This makes the jtreg tags comment complete, ready to copy and paste.

I've updated the generated javadoc for [`PassFailJFrame`](https://cr.openjdk.org/~aivanov/PassFailJFrame/api/PassFailJFrame.html); this version includes javadoc for [`WindowLayouts`](https://cr.openjdk.org/~aivanov/PassFailJFrame/api/WindowLayouts.html).

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Commit messages:
 - 8343128: PassFailJFrame.java test result: Error. Bad action for script: build}

Changes: https://git.openjdk.org/jdk/pull/21766/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21766&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8343128
  Stats: 6 lines in 1 file changed: 2 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/21766.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21766/head:pull/21766

PR: https://git.openjdk.org/jdk/pull/21766