RFR: 8237913: G1CollectedHeap::heap_region_containing shouldn't be a template.

[Thomas Schatzl]

Hi all,

  can I have reviews for this change that removes the templates and casts around `G1CollectedHeap::heap_region_containing`?

Testing: tier1-5

Thanks,
  Thomas

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Commit messages:
 - Remove some more casts
 - Revert changes to heap_region_containing()
 - Remove cast
 - Remove unnecessary changes
 - some changes
 - Use const void*

Changes: https://git.openjdk.org/jdk/pull/9572/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9572&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8237913
  Stats: 35 lines in 10 files changed: 0 ins; 10 del; 25 mod
  Patch: https://git.openjdk.org/jdk/pull/9572.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9572/head:pull/9572

PR: https://git.openjdk.org/jdk/pull/9572