RFR: 8242652: Throw SkippedException if no JS engine availabe in TestSearchScript

[Hannes Wallnöfer]

This is a simple change to throw jtreg.SkippedException if no JavaScript engine is available to run the TestSearchScript test. In my previous attempt I tried to use the SkippedException class already present elsewhere in the test tree, not realizing I couuld just copy/create the exception in the javadoc test library.

Note that while the test is skipped correctly if no JS engine is available, the test will currently fail in the presence of a JS engine such as GraalJS. This is fixed by JDK-8244535.

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Commit messages:
 - JDK-8242652: Throw SkippedException if no JS engine availabe in TestSearchScript

Changes: https://git.openjdk.java.net/jdk/pull/1412/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1412&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8242652
  Stats: 49 lines in 2 files changed: 37 ins; 10 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1412.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1412/head:pull/1412

PR: https://git.openjdk.java.net/jdk/pull/1412