RFR: 8338479: GenShen: Detemplatize ShenandoahScanRemembered

[Y. Srinivas Ramakrishna]

De-templatize ShenandoahScanRemembered and ShenandoahCardCluster, based on Roman's review feedback at https://github.com/openjdk/jdk/pull/20395/files/46638cdef26fd25c290e6f63035ff5d2f1dc3bdb#r1718773835.


**Testing:**

- [x] GHA
- [x] jtreg:tier1
- [ ] codepipeline
- [ ] SPECjbb

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

Commit messages:
 - JDK-8338479 : GenShen: Detemplatize ShenandoahScanRemembered

Changes: https://git.openjdk.org/shenandoah/pull/472/files
  Webrev: https://webrevs.openjdk.org/?repo=shenandoah&pr=472&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8338479
  Stats: 1320 lines in 10 files changed: 591 ins; 669 del; 60 mod
  Patch: https://git.openjdk.org/shenandoah/pull/472.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah.git pull/472/head:pull/472

PR: https://git.openjdk.org/shenandoah/pull/472