[lworld] RFR: 8348606: [lworld] Substitutability test may perform heap allocations

[Chen Liang]

Update substitutability test to use MethodHandles that access independent primitive/pointer instead heap reallocated copies of inlined values with an object header. Need long-term solution for user MethodHandle that accesses nested values in the future; hope the intrinsics can help in the future.

Testing: test/jdk/valhalla and test/hotspot/jtreg/*/valhalla, tier 1-3 tests running.

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Commit messages:
 - 8348606: [lworld] Substitutability test may perform heap allocations

Changes: https://git.openjdk.org/valhalla/pull/1364/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1364&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8348606
  Stats: 296 lines in 5 files changed: 274 ins; 11 del; 11 mod
  Patch: https://git.openjdk.org/valhalla/pull/1364.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1364/head:pull/1364

PR: https://git.openjdk.org/valhalla/pull/1364