[jdk18] RFR: 8278897: Alignment of heap segments is not enforced correctly [v2]

[Maurizio Cimadamore]

> This PR fixes an issue with alignment constraints not being enforced correctly on on-heap segments dereference/copy operations. Alignment of on-heap segments cannot be computed exactly, as alignment of elements in arrays is, ultimately a VM implementation detail. Because of this, alignment checks on heap segments can fail or pass depending on the platform being used.
> 
> For more details about the problem and the solution please refer to:
> https://mail.openjdk.java.net/pipermail/panama-dev/2021-November/015852.html

Maurizio Cimadamore has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:

 - Merge branch 'master' into heap-align
 - Initial push

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Changes:
  - all: https://git.openjdk.java.net/jdk18/pull/37/files
  - new: https://git.openjdk.java.net/jdk18/pull/37/files/40a3acc3..3a860afa

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk18&pr=37&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk18&pr=37&range=00-01

  Stats: 2046 lines in 116 files changed: 1430 ins; 125 del; 491 mod
  Patch: https://git.openjdk.java.net/jdk18/pull/37.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk18 pull/37/head:pull/37

PR: https://git.openjdk.java.net/jdk18/pull/37