RFR: 8328301: Convert Applet test ManualHTMLDataFlavorTest.java to main program

[Phil Race]

Convert this applet based test to a main program

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Commit messages:
 - 8328301

Changes: https://git.openjdk.org/jdk/pull/18334/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18334&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8328301
  Stats: 260 lines in 2 files changed: 15 ins; 189 del; 56 mod
  Patch: https://git.openjdk.org/jdk/pull/18334.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18334/head:pull/18334

PR: https://git.openjdk.org/jdk/pull/18334