RFR: 8307652: sealed class hierarchy graph doesn't distinguish non-sealed classes [v2]

[Chen Liang]

> `@sealedGraph` had a mechanism to render non-sealed classes differently, but it's useless because the graph nodes are not bordered. This patch converts the non-sealed classes to be rendered in italics instead.
> 
> An example of `ConstantDesc`, which has a sealed hierarchy except `DynamicConstantDesc`:
> JDK 20:
> ![image](https://user-images.githubusercontent.com/7806504/236991678-e30c181a-cb1f-407a-b3e0-f648fe2df788.png)
> 
> This patch:
> ![image](https://user-images.githubusercontent.com/7806504/236991592-affcb128-9721-45cf-860c-6292ee6a8bb6.png)

Chen Liang has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - Use an edge and node to indicate non-sealed hierarchy
 - Merge branch 'master' into fix/sealedgraph-nonsealed
 - 8307652: sealed class hierarchy graph doesn't distinguish non-sealed classes

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/13877/files
  - new: https://git.openjdk.org/jdk/pull/13877/files/cab36e65..bb2d215c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13877&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13877&range=00-01

  Stats: 99505 lines in 1624 files changed: 79242 ins; 8145 del; 12118 mod
  Patch: https://git.openjdk.org/jdk/pull/13877.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13877/head:pull/13877

PR: https://git.openjdk.org/jdk/pull/13877