RFR: JDK-8316972: Add javadoc support for restricted methods [v4]

[Hannes Wallnöfer]

> Please review a change to add support for restricted methods to JavaDoc. The bulk of this patch was contributed by @mcimadamore. It adds a warning note to the summary and details of restricted methods and a superscript to links to restricted methods, similar to what we already do with elements belonging to preview APIs. I added a summary page to list all restricted methods as well as a test.
> 
> To see the wording of this feature in context, the relevant parts of generated documentation can be reviewed here:
> 
> - [Method summary](https://cr.openjdk.org/~hannesw/8316972/api.00/java.base/java/lang/foreign/AddressLayout.html#method-summary)
> - [Method details](https://cr.openjdk.org/~hannesw/8316972/api.00/java.base/java/lang/foreign/AddressLayout.html#withTargetLayout(java.lang.foreign.MemoryLayout))
> - [Restricted Methods list](https://cr.openjdk.org/~hannesw/8316972/api.00/restricted-list.html)
> - [Restricted Methods help section](https://cr.openjdk.org/~hannesw/8316972/api.00/help-doc.html#restricted)
> 
> Since the messages for deprecated, preview, and restricted elements all use the same CSS in our default stylesheet, I decided to combine them into a single CSS rule. It is still possible to define distinct styles for these features in user-provided stylesheets.

Hannes Wallnöfer has updated the pull request incrementally with one additional commit since the last revision:

  Rename local variable

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/16188/files
  - new: https://git.openjdk.org/jdk/pull/16188/files/53c66174..cd128692

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16188&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16188&range=02-03

  Stats: 6 lines in 1 file changed: 0 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/16188.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16188/head:pull/16188

PR: https://git.openjdk.org/jdk/pull/16188