[jfx17] RFR: 8271230: Remove obsolete test classes and data files from 3DViewer sample

[Kevin Rushforth]

Remove the obsolete `apps/samples/3DViewer/src/test` directory from the 3DViewer sample, including two test classes that don't run and a set of data files that won't load. This is a follow-on cleanup bug to [JDK-8269259](https://bugs.openjdk.java.net/browse/JDK-8269259).

NOTE: this is targeted to `jfx17`.

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Commit messages:
 - 8271230: Remove obsolete test classes and data files from 3DViewer sample

Changes: https://git.openjdk.java.net/jfx/pull/587/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx&pr=587&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8271230
  Stats: 7167 lines in 16 files changed: 0 ins; 7167 del; 0 mod
  Patch: https://git.openjdk.java.net/jfx/pull/587.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/587/head:pull/587

PR: https://git.openjdk.java.net/jfx/pull/587