RFR: 8314480: Memory ordering spec updates in java.lang.ref [v32]

[Brent Christian]

> Classes in the `java.lang.ref` package would benefit from an update to bring the spec in line with how the VM already behaves. The changes would focus on _happens-before_ edges at some key points during reference processing.
> 
> A couple key things we want to be able to say are:
> - `Reference.reachabilityFence(x)` _happens-before_ reference processing occurs for 'x'.
> - `Cleaner.register()` _happens-before_ the Cleaner thread runs the registered cleaning action.
> 
> This will bring Cleaner in line (or close) with the memory visibility guarantees made for finalizers in [JLS 17.4.5](https://docs.oracle.com/javase/specs/jls/se18/html/jls-17.html#jls-17.4.5):
> _"There is a happens-before edge from the end of a constructor of an object to the start of a finalizer (§12.6) for that object."_

Brent Christian has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 69 commits:

 - Merge branch 'master' into refDocs2
 - add link to Thread.isAlive()
 - small review tweaks; shorten MemoryConsistency links
 - small grammar fixes
 - new section for finalizer memviz
 - add memviz bullet for finalization
 - remove quotes from dequeue
 - package spec updates, mostly about reference queues and dequeueing
 - move reachability section before notification; update section header
 - add details on use of reference queues; swap reachability/memviz sections
 - ... and 59 more: https://git.openjdk.org/jdk/compare/7bf1989f...d7cbf0d3

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Changes: https://git.openjdk.org/jdk/pull/16644/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16644&range=31
  Stats: 226 lines in 4 files changed: 132 ins; 19 del; 75 mod
  Patch: https://git.openjdk.org/jdk/pull/16644.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16644/head:pull/16644

PR: https://git.openjdk.org/jdk/pull/16644