RFR: 8340785: Update description of PassFailJFrame and samples

[Alexey Ivanov]

I re-worked the entire description of `PassFailJFrame`:

Add description of what UI elements it provides and how to interact with them.
Add anchors for linking to the sections.

Use `{@snippet}` instead of `<pre>{@code}</pre>` for sample code.
Use method references instead of lambdas in samples.
Document required jtreg tags to use `PassFailJFrame`.
Rename `SampleOldManualTest` to `ObsoleteManualTest`.

Provide an overview of `Builder` methods to configure `PassFailJFrame`.

As in #21145, the generated javadoc [PassFailJFrame.html](https://cr.openjdk.org/~aivanov/PassFailJFrame/api/PassFailJFrame.html) could be easier to read and review.

The current version of the generated docs contains changes from #21145 and this PR. The PRs can be integrated independently.

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Commit messages:
 - 8340785: Update description of PassFailJFrame and samples

Changes: https://git.openjdk.org/jdk/pull/21162/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21162&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8340785
  Stats: 159 lines in 1 file changed: 126 ins; 0 del; 33 mod
  Patch: https://git.openjdk.org/jdk/pull/21162.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21162/head:pull/21162

PR: https://git.openjdk.org/jdk/pull/21162