RFR: 8308088: Improve class check in CollectedHeap::is_oop [v3]

[Aleksey Shipilev]

> See the bug for more details.
> 
> Additional testing:
>  - [x] Linux x86_64 fastdebug, `tier1`
>  - [x] Linux x86_64 fastdebug, `tier2`
>  - [x] Linux x86_64 fastdebug, `tier3`

Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:

  Touchup

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/13982/files
  - new: https://git.openjdk.org/jdk/pull/13982/files/983ee9f8..961b90e1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13982&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13982&range=01-02

  Stats: 2 lines in 1 file changed: 0 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/13982.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13982/head:pull/13982

PR: https://git.openjdk.org/jdk/pull/13982