RFR: JDK-8322878: Including sealing information Class.toGenericString() [v7]

[Joe Darcy]

> As recently discussed on core libs, sealed-ness information could be included in the Class.toGenericString() output, analagous to how "modifiers" that also correspond to JVM access flags are handled.
> 
> This is the initial spec, implementation, and test updated needed for that change. If there is consensus this is a reasonable direction, I'll create the CSR, etc.

Joe Darcy 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 eight additional commits since the last revision:

 - Adjust JLS quote and update copyright.
 - Merge branch 'master' into JDK-8322878
 - Expand test cases.
 - Update spec; test sealed class structures.
 - Improve regression test.
 - Update non-sealed computation.
 - Add non-seal'ing support.
 - JDK-8322878: Including sealing information Class.toGenericString()

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/17239/files
  - new: https://git.openjdk.org/jdk/pull/17239/files/d5a451d0..4cfc4e3d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17239&range=06
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17239&range=05-06

  Stats: 17609 lines in 565 files changed: 12491 ins; 2504 del; 2614 mod
  Patch: https://git.openjdk.org/jdk/pull/17239.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17239/head:pull/17239

PR: https://git.openjdk.org/jdk/pull/17239