[jdk21u-dev] RFR: 8328248: Convert javax/swing/JSlider/6587742/bug6587742.java applet test to main

[Goetz Lindenmaier]

I backport this for parity with 21.0.9-oracle

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Commit messages:
 - Backport 86f17447362483162a5983c270e0b530d8d99354

Changes: https://git.openjdk.org/jdk21u-dev/pull/2036/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=2036&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8328248
  Stats: 332 lines in 3 files changed: 166 ins; 166 del; 0 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/2036.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/2036/head:pull/2036

PR: https://git.openjdk.org/jdk21u-dev/pull/2036