[lworld] RFR: 8346307: [lworld] Clarify identity vs value in Class, Objects, and document limitations of value objects [v9]

[Roger Riggs]

> Add APINote  and javadoc for IdentityException where it will be useful to know that identity or value objects are treated differently. 
> Simplified WeakHashMap javadoc updates for IdentityException. 
> Added note to System.identityHashCode to include value objects.
> Added to class javadoc for IdentityHashMap for value objects.

Roger Riggs has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 16 commits:

 - A few editorial changes
   Highlight that in preview-mode, Objects can have either identity or value subclasses.
 - Merge branch 'lworld' into 8346307-throws-identityexception
 - Merge branch 'lworld' into 8346307-throws-identityexception
 - "value interface" is a left over from an earlier design and is not allowed by the JEP 401 JLS.
   An interface will never have the ACC_IDENTITY modifier, hence 'isValue()' will be true but is not significant.
   Class.toGenericString() should only include the "value" prefix for record and regular classes.
   Correct the test to match the toGenericString() output.
 - Merge branch 'lworld' into 8346307-throws-identityexception
 - Merge branch 'lworld' into 8346307-throws-identityexception
 - Merge
 - Merge branch 'lworld' into 8346307-throws-identityexception
 - Merge branch 'lworld' into 8346307-throws-identityexception
 - Merge branch 'lworld' into 8346307-throws-identityexception
 - ... and 6 more: https://git.openjdk.org/valhalla/compare/81fbc414...6cbade17

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Changes: https://git.openjdk.org/valhalla/pull/1327/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1327&range=08
  Stats: 266 lines in 12 files changed: 204 ins; 17 del; 45 mod
  Patch: https://git.openjdk.org/valhalla/pull/1327.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1327/head:pull/1327

PR: https://git.openjdk.org/valhalla/pull/1327