RFR: 8283660: Convert com/sun/jndi/ldap/AbstractLdapNamingEnumeration.java finalizer to Cleaner [v3]

[Brent Christian]

> Please review this change to replace the finalizer in `AbstractLdapNamingEnumeration` with a Cleaner.
> 
> The pieces of state required for cleanup (`LdapCtx homeCtx`, `LdapResult res`, and `LdapClient enumClnt`) are moved to a static inner class . From there, the change is fairly mechanical.
> 
> Details of note: 
> 1. Some operations need to change the state values (the update() method is probably the most interesting).
> 2. Subclasses need to access `homeCtx`; I added a `homeCtx()` method to read `homeCtx` from the superclass's `state`.
> 
> The test case is based on a copy of `com/sun/jndi/ldap/blits/AddTests/AddNewEntry.java`. A more minimal test case might be possible, but this was done for expediency.
> 
> The test only confirms that the new Cleaner use does not keep the object reachable. It only tests `LdapSearchEnumeration` (not `LdapNamingEnumeration` or `LdapBindingEnumeration`, though all are subclasses of `AbstractLdapNamingEnumeration`). 
> 
> Thanks.

Brent Christian has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains ten commits:

 - Merge
 - Rename inner class to EnumCtx ; use homeCtx() in AbstractLdapNamingEnumeration for consistencty ; new instance vars can be final
 - fix whitespace
 - Merge branch 'master' into remove-finalizers
 - Test changes to test new cleaner code
 - Rename test to LdapEnumeration
 - Create copy of AddNewEntry test to test AbstractLdapNamingEnumeration Cleaner
 - Merge branch 'master' into remove-finalizers
 - Replace AbstractLdapNamingEnumeration finalizer with Cleaner

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Changes: https://git.openjdk.java.net/jdk/pull/8311/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8311&range=02
  Stats: 262 lines in 7 files changed: 194 ins; 20 del; 48 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8311.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8311/head:pull/8311

PR: https://git.openjdk.java.net/jdk/pull/8311