RFR: 8301222: Generalize check_release_entry in OopStorage [v2]

[Erik Österlund]

> When an oop handle is released to OopStorage, we want to check that its contents has been cleared appropriately, honouring the general contract with OopStorage. This is currently done with a raw access checking for null. However, the raw contents in memory might not be 0, just because the logical value is null. In particular, generational ZGC will have some low order colour bits set. This CR aims to address that.

Erik Österlund has updated the pull request incrementally with one additional commit since the last revision:

  Update src/hotspot/share/gc/shared/collectedHeap.cpp
  
  Co-authored-by: Thomas Schatzl <59967451+tschatzl at users.noreply.github.com>

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Changes:
  - all: https://git.openjdk.org/jdk/pull/12252/files
  - new: https://git.openjdk.org/jdk/pull/12252/files/a150730e..0b89d558

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12252&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12252&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/12252.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12252/head:pull/12252

PR: https://git.openjdk.org/jdk/pull/12252