RFR: 8342011: Conditionally compile ReservedHeapSpace compressed heap support

[Kim Barrett]

Please review this change to ReservedHeapSpace to conditionally include the
support for compressed oops only in 64bit builds.  This code is unused and
inapplicable in 32bit builds.  Further, it contains code that is problematic
in a 32bit build.  See the JBS issue for details.

Testing: mach5 tier1, GHA testing

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Commit messages:
 - disable coops setup for 32bit

Changes: https://git.openjdk.org/jdk/pull/21484/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21484&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8342011
  Stats: 17 lines in 2 files changed: 14 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/21484.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21484/head:pull/21484

PR: https://git.openjdk.org/jdk/pull/21484