RFR: 8349688: G1: Wrong initial optional region index when selecting candidates from retained regions [v3]

[Ivan Walulya]

> Hi,
> 
> Please review this fix to the bug in setting a region index to the optional cset. The crash happens because the incorrect `_index_in_opt_cset` refers to a region that has already been evacuated.
> 
> Testing: tier5-common-apps

Ivan Walulya has updated the pull request incrementally with one additional commit since the last revision:

  Thomas suggestion

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/23568/files
  - new: https://git.openjdk.org/jdk/pull/23568/files/7c5147a2..7fdf01fc

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=23568&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23568&range=01-02

  Stats: 2 lines in 1 file changed: 2 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/23568.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23568/head:pull/23568

PR: https://git.openjdk.org/jdk/pull/23568