RFR: 8342610: ZGC: Cleanup pre-touching code

[Stefan Karlsson]

There's a few things that we'd like to cleanup around the pre-touching code.
* Remove the dependency to ZPhysicalMemoryManager - cleans up the call site
* Remove unimplemented function pretouch_view (and its friends)
* Change type from zoffset for the iteration variable - multiple threads update it and it is not guaranteed to stay below the required ZAddressOffsetMax. I can trigger an assert here if I change the code to prime_cache in the higher address range instead of the lower and setting a max heap size that matches ZAddressOffsetMax.

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Commit messages:
 - 8342610: ZGC: Cleanup pre-touching code

Changes: https://git.openjdk.org/jdk/pull/21600/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21600&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8342610
  Stats: 38 lines in 3 files changed: 12 ins; 14 del; 12 mod
  Patch: https://git.openjdk.org/jdk/pull/21600.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21600/head:pull/21600

PR: https://git.openjdk.org/jdk/pull/21600