RFR: JDK-8325325: Breadcrumb navigation shows preview link for modules and packages

[Hannes Wallnöfer]

Please review a change to simplify generation of breadcrumb navigation links. We previously used generic methods to generate the links which didn't allow to tailor the links for our needs and was also more verbose. The change adds a protected `getBreadcrumbLink` method to `HtmlDocletWriter` which makes the link generation code much simpler.

I added a check to the existing `TestPreview` test to make sure no PREVIEW links are generated for preview elements in the sub-navigation bar.

-------------

Commit messages:
 - JDK-8325325: Breadcrumb navigation shows preview link for modules and packages

Changes: https://git.openjdk.org/jdk/pull/17809/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17809&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8325325
  Stats: 123 lines in 11 files changed: 68 ins; 34 del; 21 mod
  Patch: https://git.openjdk.org/jdk/pull/17809.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17809/head:pull/17809

PR: https://git.openjdk.org/jdk/pull/17809