RFR: 8295653: Add a graph of the sealed class hierarchy for marked classes

[Magnus Ihse Bursie]

It would be possible to mark classes with `@sealedGraph` to indicate that the sealed hierarchy should be rendered graphically in the JavaDocs. Classes not marked would be unaffected, creating an opt-in approach.

[Here](https://bugs.openjdk.org/secure/attachment/101126/Screen%20Shot%202022-10-19%20at%2012.47.47%20PM.png) is an example of MemoryLayout class rendering.

This feature has been developed in cooperation with Per Minborg.

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

Commit messages:
 - Update copyright year; remove testing annotations
 - Make sealed graphs look like module graphs
 - Fix failing test after updating css
 - FIx hover etc to match moduleGraph
 - cleanup
 - Fix problem with superclass
 - Change dotted to dashed
 - Add dotted nodes for open classes
 - Actually we *only* need to depend on the dot file...
 - Add dependency to dot file for svg file generation
 - ... and 21 more: https://git.openjdk.org/jdk/compare/fc889577...8627a08e

Changes: https://git.openjdk.org/jdk/pull/10761/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10761&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8295653
  Stats: 372 lines in 5 files changed: 324 ins; 0 del; 48 mod
  Patch: https://git.openjdk.org/jdk/pull/10761.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10761/head:pull/10761

PR: https://git.openjdk.org/jdk/pull/10761