RFR: 8364212: Shenandoah: Rework archived objects loading

[Aleksey Shipilev]

As continuation of [JDK-8293650](https://bugs.openjdk.org/browse/JDK-8293650), we would want to avoid allocating CDS archives as humongous regions and then flipping them back to regular state. This already complicates the region accounting significantly, and was a source a few bugs. We can rework the CDS archive load to cleanly ask collector for a contiguous set of regular regions.

Additional testing:
 - [x] Linux x86_64 server fastdebug, `hotspot_gc_shenandoah`
 - [x] Linux x86_64 server fastdebug, `runtime/cds`
 - [x] Linux x86_64 server fastdebug, `runtime/cds` with `-XX:+UseShenandoahGC`
 - [ ] Linux x86_64 server fastdebug, `all`

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

Commit messages:
 - Fix
 - Fix
 - Regular CDS

Changes: https://git.openjdk.org/jdk/pull/26510/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26510&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8364212
  Stats: 107 lines in 6 files changed: 35 ins; 35 del; 37 mod
  Patch: https://git.openjdk.org/jdk/pull/26510.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26510/head:pull/26510

PR: https://git.openjdk.org/jdk/pull/26510