RFR: 8255982: Extend BasicJMapTest to test with different GC Heap

[Lin Zang]

The implementation of jmap tool depends on the implementation of object iteration by different GC heap.
This patch extend the BasicJMapTest to cover differet GC Heap.

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Commit messages:
 - 8255982: Extend BasicJMapTest to test with different GC Heap

Changes: https://git.openjdk.java.net/jdk/pull/1094/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1094&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8255982
  Stats: 5 lines in 1 file changed: 4 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1094.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1094/head:pull/1094

PR: https://git.openjdk.java.net/jdk/pull/1094