[jdk21u-dev] RFR: 8327757: Convert javax/swing/JSlider/6524424/bug6524424.java applet to main

[Satyen Subramaniam]

Backporting JDK-8327757: Convert javax/swing/JSlider/6524424/bug6524424.java applet to main. Converts bug6524424 from old applet format to more modern main function approach. Ran GHA Sanity Checks and adjusted test directly. Patch is clean. Backporting for parity with Oracle.

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Commit messages:
 - Backport ac5b6cb2d42bdb8fb1a110ad33411b50cff4ea61

Changes: https://git.openjdk.org/jdk21u-dev/pull/2456/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=2456&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8327757
  Stats: 255 lines in 3 files changed: 120 ins; 135 del; 0 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/2456.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/2456/head:pull/2456

PR: https://git.openjdk.org/jdk21u-dev/pull/2456