RFR: 8359083: Test jdkCheckHtml.java should report SkippedException rather than report fails when miss tidy

[SendaoYan]

Hi all,

When there is no `tidy` command in PATH, the test test/docs/jdk/javadoc/doccheck/checks/jdkCheckHtml.java report failure, I think it shoule be report jtreg.SkippedException rather than report test failure.
In file test/docs/jdk/javadoc/doccheck/DocCheck.java, we need to call the `new TidyChecker()` before executing the test so that the `jtreg.SkippedException` exception can be thrown normally, that's why I add `new TidyChecker()` in `init()` function.

Change has been verified locally, only the test test/docs/jdk/javadoc/doccheck/checks/jdkCheckHtml.java observed this failure, test-fix only, no risk.

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Commit messages:
 - 8359083: Test jdkCheckHtml.java should report SkippedException rather than report fails when miss tidy

Changes: https://git.openjdk.org/jdk/pull/25711/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25711&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8359083
  Stats: 10 lines in 3 files changed: 4 ins; 1 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/25711.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25711/head:pull/25711

PR: https://git.openjdk.org/jdk/pull/25711