[jdk8u-ri] RFR: 8071507: (ref) Clear phantom reference as soft and weak references do [v2]

[Mandy Chung]

On Thu, 21 Apr 2022 16:05:25 GMT, Poonam Bajaj <poonam at openjdk.org> wrote:

>> These changes backport the following fixes to jdk8u-ri:
>> - 8071507: (ref) Clear phantom reference as soft and weak references do
>> - 8143847: Remove REF_CLEANER reference category
>> 
>> With these changes, phantom references are automatically cleared by the garbage collector as soft and weak references.
>
> Poonam Bajaj has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Corrected documentation in package.html

[JDK-8285096](https://bugs.openjdk.java.net/browse/JDK-8285096) is the CSR.   Looks like it was not recognized that blocked the integration.  Taking `/csr` out seems to help.

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

PR: https://git.openjdk.java.net/jdk8u-ri/pull/4