RFR: 8371284: GenShen: Avoid unnecessary card marking [v2]

[Nityanand Rai]

> Exclude young-young, old-old and honor UseCondCardMark in dirty card marking.

Nityanand Rai has updated the pull request incrementally with one additional commit since the last revision:

  early return of oop is null

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/28204/files
  - new: https://git.openjdk.org/jdk/pull/28204/files/09ad25ab..59f7a0d0

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28204&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28204&range=00-01

  Stats: 8 lines in 1 file changed: 1 ins; 1 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/28204.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28204/head:pull/28204

PR: https://git.openjdk.org/jdk/pull/28204