RFR: 8316003: Update FileChooserSymLinkTest.java to HTML instructions [v2]

[Alexey Ivanov]

> 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).

Alexey Ivanov has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains one additional commit since the last revision:

  Revert "Revert changes to FileChooserSymLinkTest.java"
  
  This reverts commit 7753b3f3e2d3a0df5fde672ad41833b6a9c6e247.

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/15661/files
  - new: https://git.openjdk.org/jdk/pull/15661/files/80fec8a4..41eaf1b8

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15661&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15661&range=00-01

  Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 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