RFR: 8316003: Update FileChooserSymLinkTest.java to HTML instructions

Mon Sep 11 13:35:07 UTC 2023

To demonstrate the functionality of HTML formatting in `PassFailJFrame`, I updated the instructions for the `test/jdk/javax/swing/JFileChooser/FileChooserSymLinkTest.java` test. The commands to create the symbolic links are marked up with monospace font, which makes them stand out. The test instructions for single- and multi-selection are emphasised with bold text.

This change depends on #15660 and [JDK-8294158](https://bugs.openjdk.org/browse/JDK-8294158).

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Commit messages:
 - Refactor configuration of a text component for instructions
 - Improve instruction formatting
 - Enable HTML display if instructions start with <html>

Changes: https://git.openjdk.org/jdk/pull/15661/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15661&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8316003
  Stats: 84 lines in 2 files changed: 48 ins; 1 del; 35 mod
  Patch: https://git.openjdk.org/jdk/pull/15661.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15661/head:pull/15661

PR: https://git.openjdk.org/jdk/pull/15661