[jdk21u-dev] RFR: 8328670: Automate and open source few closed manual applet test

[Goetz Lindenmaier]

I backport this for parity with 21.0.8-oracle.

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Commit messages:
 - Backport 38e3cda4420ef921cc6e43cb18338ec18c12011f

Changes: https://git.openjdk.org/jdk21u-dev/pull/1470/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1470&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8328670
  Stats: 291 lines in 2 files changed: 291 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1470.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1470/head:pull/1470

PR: https://git.openjdk.org/jdk21u-dev/pull/1470